Page 1
CBSE XI | Mathematics
Sample Paper – 1 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 1 Solution
SECTION – A
1. [sin(x+1)]’ = cos (x+1) .1 = cos (x+1)
2. Giving one counter example is enough to prove the falsehood of a statement. Here
counter example is: The real number 1 is neither prime nor composite. So the statement
is false.
3.
? ? ? ?
2 2 2
1 3i 1 2i 1 6 3i 2i 5 5i 5 5i 5 5i
1i
1 2i 1 2i 1 4 5
1 4i
1 2i
? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?
? ? ?
?
?
OR
i
n
+ i
n + 1
+ i
n + 2
+ i
n + 3
= i
n
(1 + i + i
2
+ i
3
) = i
n
(1 + i – 1 – i) = 0 ? i
2
= -1 and i
3
= -i
4. Sample space S = {HH, HT, TH, TT} i.e. total number of cases = 4
Favourable cases for atleast one head are {HH, HT, TH}.
Required probability =
3
4
SECTION – B
5. n(A - B) = 14 + x, n(B - A) = 3x and n(A ? B) = x
n(A) = n(B)
n(A) = n(A - B) + n(A ? B);
n(B) = n(B - A) + n(A ? B)
? n(A - B) + n(A ? B) = n(B - A) + n(A ? B)
? 14 + x + x = 3x + x
?14 = 2 x ?x = 7
Page 2
CBSE XI | Mathematics
Sample Paper – 1 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 1 Solution
SECTION – A
1. [sin(x+1)]’ = cos (x+1) .1 = cos (x+1)
2. Giving one counter example is enough to prove the falsehood of a statement. Here
counter example is: The real number 1 is neither prime nor composite. So the statement
is false.
3.
? ? ? ?
2 2 2
1 3i 1 2i 1 6 3i 2i 5 5i 5 5i 5 5i
1i
1 2i 1 2i 1 4 5
1 4i
1 2i
? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?
? ? ?
?
?
OR
i
n
+ i
n + 1
+ i
n + 2
+ i
n + 3
= i
n
(1 + i + i
2
+ i
3
) = i
n
(1 + i – 1 – i) = 0 ? i
2
= -1 and i
3
= -i
4. Sample space S = {HH, HT, TH, TT} i.e. total number of cases = 4
Favourable cases for atleast one head are {HH, HT, TH}.
Required probability =
3
4
SECTION – B
5. n(A - B) = 14 + x, n(B - A) = 3x and n(A ? B) = x
n(A) = n(B)
n(A) = n(A - B) + n(A ? B);
n(B) = n(B - A) + n(A ? B)
? n(A - B) + n(A ? B) = n(B - A) + n(A ? B)
? 14 + x + x = 3x + x
?14 = 2 x ?x = 7
CBSE XI | Mathematics
Sample Paper – 1 Solution
6. Let a be any element which belongs to set A, i.e a ? A
P(A) is the set of all subsets of the set A. Therefore {a} belongs to P(A)
i.e {a} ? P(A)
But P(A) = P(B) [ Given ]
? {a} ? P(B)
? a ? B
So a ? A ? a ? B, Hence A ? B
Similarly, we can prove that A ? B
? A = B
OR
aN = {ax : x ?N}
3N = {3x : x ? N} = {3, 6, 9,….}
And 7N = {7x : x ? N} = {7, 14, 21, 28,…}
3N n 7N = {21, 42, …} = {21x : x ? N} = 21N
7. Let A be the set of teachers who teach math and B be the set of teachers who tech
physics. Then,
n(A ? B) = 11, n(A) = 7 & n(A ? B) = 3
n(A ? B) = n(A) + n(B) - n(A ? B)
11 = 7 - n(B) + 3
n(B) = 7
OR
n(A) = 20, n(A ? B) = 42 and n(A n B) = 4
n(A ? B) = n(A) + n(B) – n(An B)
42 = 20 + n(B) – 4
n(B) = 42 – 20 + 4 = 26
n(A – B) = n(A) – n(An B)
= 20 – 4 = 16
8. A × B = {(1, 3), (1, 4), (2, 3), (2, 4)}
Since A × B contains 4 elements therefore it has 2
4
= 16 subsets
Subsets are
{ },
{(1, 3)}, {(1, 4)}, {(2, 3)}, {(2, 4)},
{(1,3), (1,4)}, {(1,3), (2,3)}, {(1,3), (2,4)}, {(1,4), (2,3)}, {(1,4), (2,4)},
{(1, 3), (1, 4), (2, 3)}, {(1, 3), (1, 4), (2, 4)}, {(1, 4), (2, 3), (2, 4)},
{(1, 3), (1, 4), (2, 3), (2, 4)}.
Page 3
CBSE XI | Mathematics
Sample Paper – 1 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 1 Solution
SECTION – A
1. [sin(x+1)]’ = cos (x+1) .1 = cos (x+1)
2. Giving one counter example is enough to prove the falsehood of a statement. Here
counter example is: The real number 1 is neither prime nor composite. So the statement
is false.
3.
? ? ? ?
2 2 2
1 3i 1 2i 1 6 3i 2i 5 5i 5 5i 5 5i
1i
1 2i 1 2i 1 4 5
1 4i
1 2i
? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?
? ? ?
?
?
OR
i
n
+ i
n + 1
+ i
n + 2
+ i
n + 3
= i
n
(1 + i + i
2
+ i
3
) = i
n
(1 + i – 1 – i) = 0 ? i
2
= -1 and i
3
= -i
4. Sample space S = {HH, HT, TH, TT} i.e. total number of cases = 4
Favourable cases for atleast one head are {HH, HT, TH}.
Required probability =
3
4
SECTION – B
5. n(A - B) = 14 + x, n(B - A) = 3x and n(A ? B) = x
n(A) = n(B)
n(A) = n(A - B) + n(A ? B);
n(B) = n(B - A) + n(A ? B)
? n(A - B) + n(A ? B) = n(B - A) + n(A ? B)
? 14 + x + x = 3x + x
?14 = 2 x ?x = 7
CBSE XI | Mathematics
Sample Paper – 1 Solution
6. Let a be any element which belongs to set A, i.e a ? A
P(A) is the set of all subsets of the set A. Therefore {a} belongs to P(A)
i.e {a} ? P(A)
But P(A) = P(B) [ Given ]
? {a} ? P(B)
? a ? B
So a ? A ? a ? B, Hence A ? B
Similarly, we can prove that A ? B
? A = B
OR
aN = {ax : x ?N}
3N = {3x : x ? N} = {3, 6, 9,….}
And 7N = {7x : x ? N} = {7, 14, 21, 28,…}
3N n 7N = {21, 42, …} = {21x : x ? N} = 21N
7. Let A be the set of teachers who teach math and B be the set of teachers who tech
physics. Then,
n(A ? B) = 11, n(A) = 7 & n(A ? B) = 3
n(A ? B) = n(A) + n(B) - n(A ? B)
11 = 7 - n(B) + 3
n(B) = 7
OR
n(A) = 20, n(A ? B) = 42 and n(A n B) = 4
n(A ? B) = n(A) + n(B) – n(An B)
42 = 20 + n(B) – 4
n(B) = 42 – 20 + 4 = 26
n(A – B) = n(A) – n(An B)
= 20 – 4 = 16
8. A × B = {(1, 3), (1, 4), (2, 3), (2, 4)}
Since A × B contains 4 elements therefore it has 2
4
= 16 subsets
Subsets are
{ },
{(1, 3)}, {(1, 4)}, {(2, 3)}, {(2, 4)},
{(1,3), (1,4)}, {(1,3), (2,3)}, {(1,3), (2,4)}, {(1,4), (2,3)}, {(1,4), (2,4)},
{(1, 3), (1, 4), (2, 3)}, {(1, 3), (1, 4), (2, 4)}, {(1, 4), (2, 3), (2, 4)},
{(1, 3), (1, 4), (2, 3), (2, 4)}.
CBSE XI | Mathematics
Sample Paper – 1 Solution
9.
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ? ? ? ?
? ? ? ?
??
? ? ? ? ? ? ? ?
??
? ? ? ?
? ? ? ?
cos A sin A cos A sin A
sin A cosA
1 tan A 1 cot A
11
cosA sin A
? ? ? ?
?
? ? ? ?
? ? ? ?
??
? ? ? ?
22
cos A sin A
cosA sin A sin A cosA
? ? ? ?
? ?
???? ??
?
?
????
??
??
?? ??
??
22
cos A sin A cos A sin A
cos A sin A
cosA sin A cosA sin A
cos A sin A
OR
cot
4
? + cot
2
? = (cot
2
?)
2
+ cot
2
?
= (cosec
2
? - 1)
2
+ cosec
2
? - 1
= cosec
4
? - 2cosec
2
? + 1 + cosec
2
? - 1
= cosec
4
? - cosec
2
?
10.
1. If a number is not divisible by 3, it is not divisible by 9.
2. If you are not citizen of India, then you were not born in India.
11. ? ? ? ? ?
3 3 3 3
The given series : 10 11 12 .. 20
? ? ? ?
??
?? ??
?
??
? ? ? ? ?
?
??
?
? ? ? ?
??
? ? ? ? ? ?
?
?
??
20 10
33
r1
3 3 3 3 3 3
r1
3
2
3
2
rr
20(
Can be written as
1 2 3 .. 20 1 2 3
20 1) 9(9
.. 9
1)
22
42075
12. ? ? ? ? ? ? ? Vertices of a parallelogram ABCD are A 4, 11 , B 5, 3 & C 2, 15
? ?
? ? ? ??
?
??
??
?? ??
?
??
??
let D x,y
4 2 11 15
then mid point of diagonal AC ,
22
5 x 3 y
also mid point of diagonal BD ,
22
Page 4
CBSE XI | Mathematics
Sample Paper – 1 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 1 Solution
SECTION – A
1. [sin(x+1)]’ = cos (x+1) .1 = cos (x+1)
2. Giving one counter example is enough to prove the falsehood of a statement. Here
counter example is: The real number 1 is neither prime nor composite. So the statement
is false.
3.
? ? ? ?
2 2 2
1 3i 1 2i 1 6 3i 2i 5 5i 5 5i 5 5i
1i
1 2i 1 2i 1 4 5
1 4i
1 2i
? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?
? ? ?
?
?
OR
i
n
+ i
n + 1
+ i
n + 2
+ i
n + 3
= i
n
(1 + i + i
2
+ i
3
) = i
n
(1 + i – 1 – i) = 0 ? i
2
= -1 and i
3
= -i
4. Sample space S = {HH, HT, TH, TT} i.e. total number of cases = 4
Favourable cases for atleast one head are {HH, HT, TH}.
Required probability =
3
4
SECTION – B
5. n(A - B) = 14 + x, n(B - A) = 3x and n(A ? B) = x
n(A) = n(B)
n(A) = n(A - B) + n(A ? B);
n(B) = n(B - A) + n(A ? B)
? n(A - B) + n(A ? B) = n(B - A) + n(A ? B)
? 14 + x + x = 3x + x
?14 = 2 x ?x = 7
CBSE XI | Mathematics
Sample Paper – 1 Solution
6. Let a be any element which belongs to set A, i.e a ? A
P(A) is the set of all subsets of the set A. Therefore {a} belongs to P(A)
i.e {a} ? P(A)
But P(A) = P(B) [ Given ]
? {a} ? P(B)
? a ? B
So a ? A ? a ? B, Hence A ? B
Similarly, we can prove that A ? B
? A = B
OR
aN = {ax : x ?N}
3N = {3x : x ? N} = {3, 6, 9,….}
And 7N = {7x : x ? N} = {7, 14, 21, 28,…}
3N n 7N = {21, 42, …} = {21x : x ? N} = 21N
7. Let A be the set of teachers who teach math and B be the set of teachers who tech
physics. Then,
n(A ? B) = 11, n(A) = 7 & n(A ? B) = 3
n(A ? B) = n(A) + n(B) - n(A ? B)
11 = 7 - n(B) + 3
n(B) = 7
OR
n(A) = 20, n(A ? B) = 42 and n(A n B) = 4
n(A ? B) = n(A) + n(B) – n(An B)
42 = 20 + n(B) – 4
n(B) = 42 – 20 + 4 = 26
n(A – B) = n(A) – n(An B)
= 20 – 4 = 16
8. A × B = {(1, 3), (1, 4), (2, 3), (2, 4)}
Since A × B contains 4 elements therefore it has 2
4
= 16 subsets
Subsets are
{ },
{(1, 3)}, {(1, 4)}, {(2, 3)}, {(2, 4)},
{(1,3), (1,4)}, {(1,3), (2,3)}, {(1,3), (2,4)}, {(1,4), (2,3)}, {(1,4), (2,4)},
{(1, 3), (1, 4), (2, 3)}, {(1, 3), (1, 4), (2, 4)}, {(1, 4), (2, 3), (2, 4)},
{(1, 3), (1, 4), (2, 3), (2, 4)}.
CBSE XI | Mathematics
Sample Paper – 1 Solution
9.
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ? ? ? ?
? ? ? ?
??
? ? ? ? ? ? ? ?
??
? ? ? ?
? ? ? ?
cos A sin A cos A sin A
sin A cosA
1 tan A 1 cot A
11
cosA sin A
? ? ? ?
?
? ? ? ?
? ? ? ?
??
? ? ? ?
22
cos A sin A
cosA sin A sin A cosA
? ? ? ?
? ?
???? ??
?
?
????
??
??
?? ??
??
22
cos A sin A cos A sin A
cos A sin A
cosA sin A cosA sin A
cos A sin A
OR
cot
4
? + cot
2
? = (cot
2
?)
2
+ cot
2
?
= (cosec
2
? - 1)
2
+ cosec
2
? - 1
= cosec
4
? - 2cosec
2
? + 1 + cosec
2
? - 1
= cosec
4
? - cosec
2
?
10.
1. If a number is not divisible by 3, it is not divisible by 9.
2. If you are not citizen of India, then you were not born in India.
11. ? ? ? ? ?
3 3 3 3
The given series : 10 11 12 .. 20
? ? ? ?
??
?? ??
?
??
? ? ? ? ?
?
??
?
? ? ? ?
??
? ? ? ? ? ?
?
?
??
20 10
33
r1
3 3 3 3 3 3
r1
3
2
3
2
rr
20(
Can be written as
1 2 3 .. 20 1 2 3
20 1) 9(9
.. 9
1)
22
42075
12. ? ? ? ? ? ? ? Vertices of a parallelogram ABCD are A 4, 11 , B 5, 3 & C 2, 15
? ?
? ? ? ??
?
??
??
?? ??
?
??
??
let D x,y
4 2 11 15
then mid point of diagonal AC ,
22
5 x 3 y
also mid point of diagonal BD ,
22
CBSE XI | Mathematics
Sample Paper – 1 Solution
? ? ? ? ? ? ? ? ?
?
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ? ?
but midpoint of AC BD coincides
so,
4 2 11 15 5 x 3 y
,,
2 2 2 2
5 x 4 2........... x 1
3 y 11 15......... y 1
SECTION – C
13. f(x) 2x 1,g(x) 2x 3;x R ? ? ? ? ?
? ? ? ? ? ?
? ? ? ? ? ?
? ? ? ?
22
f g (x) f(x) g(x) 2x 1 2x 3 4x 2;x R
f g (x) f(x) g(x) 2x 1 2x 3 4
(fg)(x) f(x)g(x) 2x 1 2x 3 4x 2x 6x 3 4x 4x 3
f f(x) 2x 1 3
(x) ;x R
g g(x) 2x 3 2
? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? ?
?? ? ??
? ? ? ? ?
??
??
?
?? ??
14.
{(a, b), a = b
4
, a, b ? N}
(i) (a, a) ? R ? a = a
4
,
which is true for a = 1 only, not for other values of a ? N
? Relation is not reflexive
(ii) {(a, b), a = b
4
, a, b ? N} and {(b, a),
b = a
4
, a, b ? N}
a = b
4
and b =
a
4
cannot be true simultaneously
? Relation is not symmetric.
(iii) {(a, b), a =b
4
, a, b ? N}; {(b, c), b =c
4
, b, c ?N}
? a = b
4
= c
16
So a ? c
4
? (a, c) ? R
? Relation is not transitive.
(iv) Since the relation is not reflexive, not symmetric, and also not transitive,
? Relation is not an equivalence relation
15. We know,
2 2 2
2 2 2
b c a 25 49 9 65 13
cos A =
2bc 2(5)(7) 70 14
a c b 9 49 25 33
cos B =
2ac 2(3)(7) 42
? ? ? ?
? ? ?
? ? ? ?
??
Page 5
CBSE XI | Mathematics
Sample Paper – 1 Solution
CBSE Board
Class XI Mathematics
Sample Paper – 1 Solution
SECTION – A
1. [sin(x+1)]’ = cos (x+1) .1 = cos (x+1)
2. Giving one counter example is enough to prove the falsehood of a statement. Here
counter example is: The real number 1 is neither prime nor composite. So the statement
is false.
3.
? ? ? ?
2 2 2
1 3i 1 2i 1 6 3i 2i 5 5i 5 5i 5 5i
1i
1 2i 1 2i 1 4 5
1 4i
1 2i
? ? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ?
? ? ?
?
?
OR
i
n
+ i
n + 1
+ i
n + 2
+ i
n + 3
= i
n
(1 + i + i
2
+ i
3
) = i
n
(1 + i – 1 – i) = 0 ? i
2
= -1 and i
3
= -i
4. Sample space S = {HH, HT, TH, TT} i.e. total number of cases = 4
Favourable cases for atleast one head are {HH, HT, TH}.
Required probability =
3
4
SECTION – B
5. n(A - B) = 14 + x, n(B - A) = 3x and n(A ? B) = x
n(A) = n(B)
n(A) = n(A - B) + n(A ? B);
n(B) = n(B - A) + n(A ? B)
? n(A - B) + n(A ? B) = n(B - A) + n(A ? B)
? 14 + x + x = 3x + x
?14 = 2 x ?x = 7
CBSE XI | Mathematics
Sample Paper – 1 Solution
6. Let a be any element which belongs to set A, i.e a ? A
P(A) is the set of all subsets of the set A. Therefore {a} belongs to P(A)
i.e {a} ? P(A)
But P(A) = P(B) [ Given ]
? {a} ? P(B)
? a ? B
So a ? A ? a ? B, Hence A ? B
Similarly, we can prove that A ? B
? A = B
OR
aN = {ax : x ?N}
3N = {3x : x ? N} = {3, 6, 9,….}
And 7N = {7x : x ? N} = {7, 14, 21, 28,…}
3N n 7N = {21, 42, …} = {21x : x ? N} = 21N
7. Let A be the set of teachers who teach math and B be the set of teachers who tech
physics. Then,
n(A ? B) = 11, n(A) = 7 & n(A ? B) = 3
n(A ? B) = n(A) + n(B) - n(A ? B)
11 = 7 - n(B) + 3
n(B) = 7
OR
n(A) = 20, n(A ? B) = 42 and n(A n B) = 4
n(A ? B) = n(A) + n(B) – n(An B)
42 = 20 + n(B) – 4
n(B) = 42 – 20 + 4 = 26
n(A – B) = n(A) – n(An B)
= 20 – 4 = 16
8. A × B = {(1, 3), (1, 4), (2, 3), (2, 4)}
Since A × B contains 4 elements therefore it has 2
4
= 16 subsets
Subsets are
{ },
{(1, 3)}, {(1, 4)}, {(2, 3)}, {(2, 4)},
{(1,3), (1,4)}, {(1,3), (2,3)}, {(1,3), (2,4)}, {(1,4), (2,3)}, {(1,4), (2,4)},
{(1, 3), (1, 4), (2, 3)}, {(1, 3), (1, 4), (2, 4)}, {(1, 4), (2, 3), (2, 4)},
{(1, 3), (1, 4), (2, 3), (2, 4)}.
CBSE XI | Mathematics
Sample Paper – 1 Solution
9.
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ? ? ? ?
? ? ? ?
??
? ? ? ? ? ? ? ?
??
? ? ? ?
? ? ? ?
cos A sin A cos A sin A
sin A cosA
1 tan A 1 cot A
11
cosA sin A
? ? ? ?
?
? ? ? ?
? ? ? ?
??
? ? ? ?
22
cos A sin A
cosA sin A sin A cosA
? ? ? ?
? ?
???? ??
?
?
????
??
??
?? ??
??
22
cos A sin A cos A sin A
cos A sin A
cosA sin A cosA sin A
cos A sin A
OR
cot
4
? + cot
2
? = (cot
2
?)
2
+ cot
2
?
= (cosec
2
? - 1)
2
+ cosec
2
? - 1
= cosec
4
? - 2cosec
2
? + 1 + cosec
2
? - 1
= cosec
4
? - cosec
2
?
10.
1. If a number is not divisible by 3, it is not divisible by 9.
2. If you are not citizen of India, then you were not born in India.
11. ? ? ? ? ?
3 3 3 3
The given series : 10 11 12 .. 20
? ? ? ?
??
?? ??
?
??
? ? ? ? ?
?
??
?
? ? ? ?
??
? ? ? ? ? ?
?
?
??
20 10
33
r1
3 3 3 3 3 3
r1
3
2
3
2
rr
20(
Can be written as
1 2 3 .. 20 1 2 3
20 1) 9(9
.. 9
1)
22
42075
12. ? ? ? ? ? ? ? Vertices of a parallelogram ABCD are A 4, 11 , B 5, 3 & C 2, 15
? ?
? ? ? ??
?
??
??
?? ??
?
??
??
let D x,y
4 2 11 15
then mid point of diagonal AC ,
22
5 x 3 y
also mid point of diagonal BD ,
22
CBSE XI | Mathematics
Sample Paper – 1 Solution
? ? ? ? ? ? ? ? ?
?
? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ? ?
but midpoint of AC BD coincides
so,
4 2 11 15 5 x 3 y
,,
2 2 2 2
5 x 4 2........... x 1
3 y 11 15......... y 1
SECTION – C
13. f(x) 2x 1,g(x) 2x 3;x R ? ? ? ? ?
? ? ? ? ? ?
? ? ? ? ? ?
? ? ? ?
22
f g (x) f(x) g(x) 2x 1 2x 3 4x 2;x R
f g (x) f(x) g(x) 2x 1 2x 3 4
(fg)(x) f(x)g(x) 2x 1 2x 3 4x 2x 6x 3 4x 4x 3
f f(x) 2x 1 3
(x) ;x R
g g(x) 2x 3 2
? ? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ?
? ? ? ? ? ? ? ? ? ? ?
?? ? ??
? ? ? ? ?
??
??
?
?? ??
14.
{(a, b), a = b
4
, a, b ? N}
(i) (a, a) ? R ? a = a
4
,
which is true for a = 1 only, not for other values of a ? N
? Relation is not reflexive
(ii) {(a, b), a = b
4
, a, b ? N} and {(b, a),
b = a
4
, a, b ? N}
a = b
4
and b =
a
4
cannot be true simultaneously
? Relation is not symmetric.
(iii) {(a, b), a =b
4
, a, b ? N}; {(b, c), b =c
4
, b, c ?N}
? a = b
4
= c
16
So a ? c
4
? (a, c) ? R
? Relation is not transitive.
(iv) Since the relation is not reflexive, not symmetric, and also not transitive,
? Relation is not an equivalence relation
15. We know,
2 2 2
2 2 2
b c a 25 49 9 65 13
cos A =
2bc 2(5)(7) 70 14
a c b 9 49 25 33
cos B =
2ac 2(3)(7) 42
? ? ? ?
? ? ?
? ? ? ?
??
CBSE XI | Mathematics
Sample Paper – 1 Solution
16. Let 5 12i x yi ? ? ?
? ?
22
5 12i x y 2xy i ? ? ? ? ?
Equating real and imaginary parts, we get
x
2
– y
2
= 5…….(i) and
2xy = -12..…….(ii)
Now (x
2
+ y
2
)
2
= (x
2
- y
2
)
2
+ (2xy)
2
= 5
2
+ 12
2
= 169
? x
2
+ y
2
= 13 ………………..(iii)
From (i) and (iii), we get
2x
2
= 18 ? x = ? 3
and y = ? 2
From equation (ii) we can say that xy is negative.
As xy is negative ? when x = 3, y = -2
and when x = -3, y = 2
The required square roots are (3 - 2i) and (-3 + 2i)
or ? (3 - 2i)
17. Total number of possible sets of 7 cards =
52
C7
Number of sets of 7 with all 4 aces =
4
C4 ?
48
C3
(4 aces from among 4 aces and other 3 cards must be chosen from the rest 48 cards)
Hence the probability that the 7 cards drawn contain 4 aces =
4 48
43
52
7
CC
C
?
=
1
7735
18. We have
2 3 4 5 6 3 5 2 4 6
2
22
1 1 1 1 1 1 1 1 1 1 1 1
33
5 3 5 3 5 3 3 5 5 5
1
1
1 9 1 25
35
11
3 8 25 24
11
35
3 1 10 5
8 24 24 12
? ? ? ?
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
? ? ? ?
? ? ? ?
? ? ? ? ? ?
??
? ? ? ?
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