Page 1
8
th
January 2020 (Shift 1), Mathematics Page | 1
Date: 8
th
January 2020 (Shift 1)
Time: 9:30 A.M. to 12:30 P.M.
Subject: Mathematics
1. The maximum values of ??
19
?? , ??
20
?? , ??
21
?? are ?? ,?? ,?? respectively. Then, the relation
between ?? ,?? ,?? is
a.
?? 22
=
?? 42
=
?? 11
b.
?? 11
=
?? 22
=
?? 42
c.
?? 22
=
?? 11
=
?? 42
d.
?? 21
=
?? 11
=
?? 22
Answer: ( ?? )
Solution:
We know that, ??
?? ?? is maximum when ?? = {
?? 2
, ?? is even
?? +1
2
or
?? -1
2
,?? is odd
Therefore, max( ??
19
?? )= ??
19
9
= ??
max( ??
20
?? )= ??
20
10
= ??
max( ??
21
?? )= ??
21
11
= ??
?
?? ??
19
9
=
?? 20
10
× ??
19
9
=
?? 21
11
×
20
10
× ??
19
9
?? 1
=
?? 2
=
?? 42
11
?
?? 11
=
?? 22
=
?? 42
.
2. Let ?? ( ?? )=
1
3
,?? ( ?? )=
1
6
where ?? and ?? are independent events, then
a. ?? (
?? ?? )=
2
3
b. ?? (
?? ?? '
)=
5
6
c. ?? (
?? ?? '
)=
1
3
d. ?? (
?? ?? )=
1
6
Answer: ( ?? )
Solution:
If ?? and ?? are independent events, then
?? (
?? ?? )=
?? ( ?? n ?? )
?? ( ?? )
=
?? ( ?? ) ?? ( ?? )
?? ( ?? )
= ?? ( ?? )
Page 2
8
th
January 2020 (Shift 1), Mathematics Page | 1
Date: 8
th
January 2020 (Shift 1)
Time: 9:30 A.M. to 12:30 P.M.
Subject: Mathematics
1. The maximum values of ??
19
?? , ??
20
?? , ??
21
?? are ?? ,?? ,?? respectively. Then, the relation
between ?? ,?? ,?? is
a.
?? 22
=
?? 42
=
?? 11
b.
?? 11
=
?? 22
=
?? 42
c.
?? 22
=
?? 11
=
?? 42
d.
?? 21
=
?? 11
=
?? 22
Answer: ( ?? )
Solution:
We know that, ??
?? ?? is maximum when ?? = {
?? 2
, ?? is even
?? +1
2
or
?? -1
2
,?? is odd
Therefore, max( ??
19
?? )= ??
19
9
= ??
max( ??
20
?? )= ??
20
10
= ??
max( ??
21
?? )= ??
21
11
= ??
?
?? ??
19
9
=
?? 20
10
× ??
19
9
=
?? 21
11
×
20
10
× ??
19
9
?? 1
=
?? 2
=
?? 42
11
?
?? 11
=
?? 22
=
?? 42
.
2. Let ?? ( ?? )=
1
3
,?? ( ?? )=
1
6
where ?? and ?? are independent events, then
a. ?? (
?? ?? )=
2
3
b. ?? (
?? ?? '
)=
5
6
c. ?? (
?? ?? '
)=
1
3
d. ?? (
?? ?? )=
1
6
Answer: ( ?? )
Solution:
If ?? and ?? are independent events, then
?? (
?? ?? )=
?? ( ?? n ?? )
?? ( ?? )
=
?? ( ?? ) ?? ( ?? )
?? ( ?? )
= ?? ( ?? )
8
th
January 2020 (Shift 1), Mathematics Page | 2
Therefore, ?? (
?? ?? )= ?? ( ?? )=
1
3
? ?? (
?? ?? '
)= ?? ( ?? )=
1
3
.
3. If ?? ( ?? ) =
8
2?? -8
-2?? 8
2?? +8
-2?? , then inverse of ?? ( ?? ) is
a.
1
2
log
8
(
1+?? 1-?? )
b.
1
2
log
8
(
1-?? 1+?? )
c.
1
4
log
8
(
1-?? 1+?? ) d.
1
4
log
8
(
1+?? 1-?? )
Answer: ( ?? )
Solution:
?? ( ?? )=
8
2?? - 8
-2?? 8
2?? + 8
-2?? =
8
4?? - 1
8
4?? + 1
Put ?? =
8
4?? -1
8
4?? +1
Applying componendo-dividendo on both sides
?? + 1
?? - 1
=
2× 8
4?? -2
?? +1
?? -1
= -8
4?? ? 8
4?? =
1+?? 1-??
? ?? =
1
4
log
8
(
1+?? 1-?? )
?? -1
( ?? )=
1
4
log
8
(
1+?? 1-?? ) .
4. Roots of the equation ?? 2
+ ???? + 45 = 0,?? ? ?? lies on the curve |?? + 1| = 2v10, where ??
is a complex number, then
a. ?? 2
+ ?? = 12 b. ?? 2
- ?? = 36
c. ?? 2
- ?? = 30 d. ?? 2
+ ?? = 30
Answer: ( ?? )
Solution:
Given ?? 2
+ ???? + 45 = 0,?? ? ?? , let roots of the equation be ?? ± ????
Then, sum of roots = 2?? = -??
Product of roots = ?? 2
+ ?? 2
= 45
As ?? ± ???? lies on |?? + 1| = 2v10, we get
( ?? + 1)
2
+ ?? 2
= 40
? ?? 2
+ ?? 2
+ 2?? + 1 = 40
Page 3
8
th
January 2020 (Shift 1), Mathematics Page | 1
Date: 8
th
January 2020 (Shift 1)
Time: 9:30 A.M. to 12:30 P.M.
Subject: Mathematics
1. The maximum values of ??
19
?? , ??
20
?? , ??
21
?? are ?? ,?? ,?? respectively. Then, the relation
between ?? ,?? ,?? is
a.
?? 22
=
?? 42
=
?? 11
b.
?? 11
=
?? 22
=
?? 42
c.
?? 22
=
?? 11
=
?? 42
d.
?? 21
=
?? 11
=
?? 22
Answer: ( ?? )
Solution:
We know that, ??
?? ?? is maximum when ?? = {
?? 2
, ?? is even
?? +1
2
or
?? -1
2
,?? is odd
Therefore, max( ??
19
?? )= ??
19
9
= ??
max( ??
20
?? )= ??
20
10
= ??
max( ??
21
?? )= ??
21
11
= ??
?
?? ??
19
9
=
?? 20
10
× ??
19
9
=
?? 21
11
×
20
10
× ??
19
9
?? 1
=
?? 2
=
?? 42
11
?
?? 11
=
?? 22
=
?? 42
.
2. Let ?? ( ?? )=
1
3
,?? ( ?? )=
1
6
where ?? and ?? are independent events, then
a. ?? (
?? ?? )=
2
3
b. ?? (
?? ?? '
)=
5
6
c. ?? (
?? ?? '
)=
1
3
d. ?? (
?? ?? )=
1
6
Answer: ( ?? )
Solution:
If ?? and ?? are independent events, then
?? (
?? ?? )=
?? ( ?? n ?? )
?? ( ?? )
=
?? ( ?? ) ?? ( ?? )
?? ( ?? )
= ?? ( ?? )
8
th
January 2020 (Shift 1), Mathematics Page | 2
Therefore, ?? (
?? ?? )= ?? ( ?? )=
1
3
? ?? (
?? ?? '
)= ?? ( ?? )=
1
3
.
3. If ?? ( ?? ) =
8
2?? -8
-2?? 8
2?? +8
-2?? , then inverse of ?? ( ?? ) is
a.
1
2
log
8
(
1+?? 1-?? )
b.
1
2
log
8
(
1-?? 1+?? )
c.
1
4
log
8
(
1-?? 1+?? ) d.
1
4
log
8
(
1+?? 1-?? )
Answer: ( ?? )
Solution:
?? ( ?? )=
8
2?? - 8
-2?? 8
2?? + 8
-2?? =
8
4?? - 1
8
4?? + 1
Put ?? =
8
4?? -1
8
4?? +1
Applying componendo-dividendo on both sides
?? + 1
?? - 1
=
2× 8
4?? -2
?? +1
?? -1
= -8
4?? ? 8
4?? =
1+?? 1-??
? ?? =
1
4
log
8
(
1+?? 1-?? )
?? -1
( ?? )=
1
4
log
8
(
1+?? 1-?? ) .
4. Roots of the equation ?? 2
+ ???? + 45 = 0,?? ? ?? lies on the curve |?? + 1| = 2v10, where ??
is a complex number, then
a. ?? 2
+ ?? = 12 b. ?? 2
- ?? = 36
c. ?? 2
- ?? = 30 d. ?? 2
+ ?? = 30
Answer: ( ?? )
Solution:
Given ?? 2
+ ???? + 45 = 0,?? ? ?? , let roots of the equation be ?? ± ????
Then, sum of roots = 2?? = -??
Product of roots = ?? 2
+ ?? 2
= 45
As ?? ± ???? lies on |?? + 1| = 2v10, we get
( ?? + 1)
2
+ ?? 2
= 40
? ?? 2
+ ?? 2
+ 2?? + 1 = 40
8
th
January 2020 (Shift 1), Mathematics Page | 3
? 45- ?? + 1 = 40
? ?? = 6
? ?? 2
- ?? = 30.
5. Rolle’s theorem is applicable on ?? ( ?? )= ln(
?? 2
+?? 7?? ) in [3,4]. The value of ?? '' ( ?? ) is equal
to
a.
1
12
b.
-1
12
c.
-1
6
d.
1
6
Answer: ( ?? )
Solution:
Rolle’s theorem is applicable on ?? ( ?? ) in [3,4]
? ?? ( 3)= ?? ( 4)
? ln(
9 + ?? 21
)= ln(
16+ ?? 28
)
?
9+ ?? 21
=
16+ ?? 28
? 36+ 4?? = 48+ 3??
? ?? = 12
Now,
?? ( ?? )= ln(
?? 2
+ 12
7?? )? ?? '
( ?? )=
7?? ?? 2
+ 12
×
7?? × 2?? - ( ?? 2
+ 12)× 7
( 7?? )
2
?? '
( ?? )=
?? 2
- 12
?? ( ?? 2
+ 12)
?? '
( ?? )= 0 ? ?? = 2v3
?? ''
( ?? )=
-?? 4
+ 48?? 2
+ 144
?? 2
( ?? 2
+ 12)
2
?? ''
( ?? )=
1
12
.
6. Let ?? ( ?? )= ?? cos
-1
( sin ( -|?? |) ),?? ? ( -
?? 2
,
?? 2
) , then
a. ?? '
( 0)= -
?? 2
b. ?? '
( ?? ) is not defined at ?? = 0
c. ?? '
( ?? ) is decreasing in ( -
?? 2
, 0) and ?? '
( ?? ) is decreasing in ( 0,
?? 2
)
d. ?? '
( ?? ) is increasing in ( -
?? 2
, 0) and ?? '( ?? ) is increasing in ( 0,
?? 2
)
Page 4
8
th
January 2020 (Shift 1), Mathematics Page | 1
Date: 8
th
January 2020 (Shift 1)
Time: 9:30 A.M. to 12:30 P.M.
Subject: Mathematics
1. The maximum values of ??
19
?? , ??
20
?? , ??
21
?? are ?? ,?? ,?? respectively. Then, the relation
between ?? ,?? ,?? is
a.
?? 22
=
?? 42
=
?? 11
b.
?? 11
=
?? 22
=
?? 42
c.
?? 22
=
?? 11
=
?? 42
d.
?? 21
=
?? 11
=
?? 22
Answer: ( ?? )
Solution:
We know that, ??
?? ?? is maximum when ?? = {
?? 2
, ?? is even
?? +1
2
or
?? -1
2
,?? is odd
Therefore, max( ??
19
?? )= ??
19
9
= ??
max( ??
20
?? )= ??
20
10
= ??
max( ??
21
?? )= ??
21
11
= ??
?
?? ??
19
9
=
?? 20
10
× ??
19
9
=
?? 21
11
×
20
10
× ??
19
9
?? 1
=
?? 2
=
?? 42
11
?
?? 11
=
?? 22
=
?? 42
.
2. Let ?? ( ?? )=
1
3
,?? ( ?? )=
1
6
where ?? and ?? are independent events, then
a. ?? (
?? ?? )=
2
3
b. ?? (
?? ?? '
)=
5
6
c. ?? (
?? ?? '
)=
1
3
d. ?? (
?? ?? )=
1
6
Answer: ( ?? )
Solution:
If ?? and ?? are independent events, then
?? (
?? ?? )=
?? ( ?? n ?? )
?? ( ?? )
=
?? ( ?? ) ?? ( ?? )
?? ( ?? )
= ?? ( ?? )
8
th
January 2020 (Shift 1), Mathematics Page | 2
Therefore, ?? (
?? ?? )= ?? ( ?? )=
1
3
? ?? (
?? ?? '
)= ?? ( ?? )=
1
3
.
3. If ?? ( ?? ) =
8
2?? -8
-2?? 8
2?? +8
-2?? , then inverse of ?? ( ?? ) is
a.
1
2
log
8
(
1+?? 1-?? )
b.
1
2
log
8
(
1-?? 1+?? )
c.
1
4
log
8
(
1-?? 1+?? ) d.
1
4
log
8
(
1+?? 1-?? )
Answer: ( ?? )
Solution:
?? ( ?? )=
8
2?? - 8
-2?? 8
2?? + 8
-2?? =
8
4?? - 1
8
4?? + 1
Put ?? =
8
4?? -1
8
4?? +1
Applying componendo-dividendo on both sides
?? + 1
?? - 1
=
2× 8
4?? -2
?? +1
?? -1
= -8
4?? ? 8
4?? =
1+?? 1-??
? ?? =
1
4
log
8
(
1+?? 1-?? )
?? -1
( ?? )=
1
4
log
8
(
1+?? 1-?? ) .
4. Roots of the equation ?? 2
+ ???? + 45 = 0,?? ? ?? lies on the curve |?? + 1| = 2v10, where ??
is a complex number, then
a. ?? 2
+ ?? = 12 b. ?? 2
- ?? = 36
c. ?? 2
- ?? = 30 d. ?? 2
+ ?? = 30
Answer: ( ?? )
Solution:
Given ?? 2
+ ???? + 45 = 0,?? ? ?? , let roots of the equation be ?? ± ????
Then, sum of roots = 2?? = -??
Product of roots = ?? 2
+ ?? 2
= 45
As ?? ± ???? lies on |?? + 1| = 2v10, we get
( ?? + 1)
2
+ ?? 2
= 40
? ?? 2
+ ?? 2
+ 2?? + 1 = 40
8
th
January 2020 (Shift 1), Mathematics Page | 3
? 45- ?? + 1 = 40
? ?? = 6
? ?? 2
- ?? = 30.
5. Rolle’s theorem is applicable on ?? ( ?? )= ln(
?? 2
+?? 7?? ) in [3,4]. The value of ?? '' ( ?? ) is equal
to
a.
1
12
b.
-1
12
c.
-1
6
d.
1
6
Answer: ( ?? )
Solution:
Rolle’s theorem is applicable on ?? ( ?? ) in [3,4]
? ?? ( 3)= ?? ( 4)
? ln(
9 + ?? 21
)= ln(
16+ ?? 28
)
?
9+ ?? 21
=
16+ ?? 28
? 36+ 4?? = 48+ 3??
? ?? = 12
Now,
?? ( ?? )= ln(
?? 2
+ 12
7?? )? ?? '
( ?? )=
7?? ?? 2
+ 12
×
7?? × 2?? - ( ?? 2
+ 12)× 7
( 7?? )
2
?? '
( ?? )=
?? 2
- 12
?? ( ?? 2
+ 12)
?? '
( ?? )= 0 ? ?? = 2v3
?? ''
( ?? )=
-?? 4
+ 48?? 2
+ 144
?? 2
( ?? 2
+ 12)
2
?? ''
( ?? )=
1
12
.
6. Let ?? ( ?? )= ?? cos
-1
( sin ( -|?? |) ),?? ? ( -
?? 2
,
?? 2
) , then
a. ?? '
( 0)= -
?? 2
b. ?? '
( ?? ) is not defined at ?? = 0
c. ?? '
( ?? ) is decreasing in ( -
?? 2
, 0) and ?? '
( ?? ) is decreasing in ( 0,
?? 2
)
d. ?? '
( ?? ) is increasing in ( -
?? 2
, 0) and ?? '( ?? ) is increasing in ( 0,
?? 2
)
8
th
January 2020 (Shift 1), Mathematics Page | 4
Answer: ( ?? )
Solution:
?? ( ?? )= ?? cos
-1
( sin ( -|?? |) )
? ?? ( ?? )= ?? cos
-1
( -sin|?? |)
? ?? ( ?? )= ?? [?? - cos
-1
( sin|?? |) ]
? ?? ( ?? )= ?? [?? - (
?? 2
- sin
-1
( sin|?? |) ) ]
? ?? ( ?? )= ?? (
?? 2
+ |?? |)
? ?? ( ?? )= {
?? (
?? 2
+ ?? ), ?? = 0
?? (
?? 2
- ?? ), ?? < 0
? ?? '( ?? )= {
(
?? 2
+ 2?? ), ?? = 0
(
?? 2
- 2?? ), ?? < 0
Therefore, ?? '( ?? ) is decreasing ( -
?? 2
,0) and increasing in ( 0,
?? 2
) .
7. Ellipse 2?? 2
+ ?? 2
= 1 and ?? = ???? meet at a point ?? in the first quadrant. Normal to the
ellipse at ?? meets ?? -axis at ( -
1
3v2
,0) and ?? -axis at ( 0,?? ) , then |?? | is
a.
2
3
b.
2v2
3
c.
v2
3
d.
2
v3
Answer: ( ?? )
Solution:
Page 5
8
th
January 2020 (Shift 1), Mathematics Page | 1
Date: 8
th
January 2020 (Shift 1)
Time: 9:30 A.M. to 12:30 P.M.
Subject: Mathematics
1. The maximum values of ??
19
?? , ??
20
?? , ??
21
?? are ?? ,?? ,?? respectively. Then, the relation
between ?? ,?? ,?? is
a.
?? 22
=
?? 42
=
?? 11
b.
?? 11
=
?? 22
=
?? 42
c.
?? 22
=
?? 11
=
?? 42
d.
?? 21
=
?? 11
=
?? 22
Answer: ( ?? )
Solution:
We know that, ??
?? ?? is maximum when ?? = {
?? 2
, ?? is even
?? +1
2
or
?? -1
2
,?? is odd
Therefore, max( ??
19
?? )= ??
19
9
= ??
max( ??
20
?? )= ??
20
10
= ??
max( ??
21
?? )= ??
21
11
= ??
?
?? ??
19
9
=
?? 20
10
× ??
19
9
=
?? 21
11
×
20
10
× ??
19
9
?? 1
=
?? 2
=
?? 42
11
?
?? 11
=
?? 22
=
?? 42
.
2. Let ?? ( ?? )=
1
3
,?? ( ?? )=
1
6
where ?? and ?? are independent events, then
a. ?? (
?? ?? )=
2
3
b. ?? (
?? ?? '
)=
5
6
c. ?? (
?? ?? '
)=
1
3
d. ?? (
?? ?? )=
1
6
Answer: ( ?? )
Solution:
If ?? and ?? are independent events, then
?? (
?? ?? )=
?? ( ?? n ?? )
?? ( ?? )
=
?? ( ?? ) ?? ( ?? )
?? ( ?? )
= ?? ( ?? )
8
th
January 2020 (Shift 1), Mathematics Page | 2
Therefore, ?? (
?? ?? )= ?? ( ?? )=
1
3
? ?? (
?? ?? '
)= ?? ( ?? )=
1
3
.
3. If ?? ( ?? ) =
8
2?? -8
-2?? 8
2?? +8
-2?? , then inverse of ?? ( ?? ) is
a.
1
2
log
8
(
1+?? 1-?? )
b.
1
2
log
8
(
1-?? 1+?? )
c.
1
4
log
8
(
1-?? 1+?? ) d.
1
4
log
8
(
1+?? 1-?? )
Answer: ( ?? )
Solution:
?? ( ?? )=
8
2?? - 8
-2?? 8
2?? + 8
-2?? =
8
4?? - 1
8
4?? + 1
Put ?? =
8
4?? -1
8
4?? +1
Applying componendo-dividendo on both sides
?? + 1
?? - 1
=
2× 8
4?? -2
?? +1
?? -1
= -8
4?? ? 8
4?? =
1+?? 1-??
? ?? =
1
4
log
8
(
1+?? 1-?? )
?? -1
( ?? )=
1
4
log
8
(
1+?? 1-?? ) .
4. Roots of the equation ?? 2
+ ???? + 45 = 0,?? ? ?? lies on the curve |?? + 1| = 2v10, where ??
is a complex number, then
a. ?? 2
+ ?? = 12 b. ?? 2
- ?? = 36
c. ?? 2
- ?? = 30 d. ?? 2
+ ?? = 30
Answer: ( ?? )
Solution:
Given ?? 2
+ ???? + 45 = 0,?? ? ?? , let roots of the equation be ?? ± ????
Then, sum of roots = 2?? = -??
Product of roots = ?? 2
+ ?? 2
= 45
As ?? ± ???? lies on |?? + 1| = 2v10, we get
( ?? + 1)
2
+ ?? 2
= 40
? ?? 2
+ ?? 2
+ 2?? + 1 = 40
8
th
January 2020 (Shift 1), Mathematics Page | 3
? 45- ?? + 1 = 40
? ?? = 6
? ?? 2
- ?? = 30.
5. Rolle’s theorem is applicable on ?? ( ?? )= ln(
?? 2
+?? 7?? ) in [3,4]. The value of ?? '' ( ?? ) is equal
to
a.
1
12
b.
-1
12
c.
-1
6
d.
1
6
Answer: ( ?? )
Solution:
Rolle’s theorem is applicable on ?? ( ?? ) in [3,4]
? ?? ( 3)= ?? ( 4)
? ln(
9 + ?? 21
)= ln(
16+ ?? 28
)
?
9+ ?? 21
=
16+ ?? 28
? 36+ 4?? = 48+ 3??
? ?? = 12
Now,
?? ( ?? )= ln(
?? 2
+ 12
7?? )? ?? '
( ?? )=
7?? ?? 2
+ 12
×
7?? × 2?? - ( ?? 2
+ 12)× 7
( 7?? )
2
?? '
( ?? )=
?? 2
- 12
?? ( ?? 2
+ 12)
?? '
( ?? )= 0 ? ?? = 2v3
?? ''
( ?? )=
-?? 4
+ 48?? 2
+ 144
?? 2
( ?? 2
+ 12)
2
?? ''
( ?? )=
1
12
.
6. Let ?? ( ?? )= ?? cos
-1
( sin ( -|?? |) ),?? ? ( -
?? 2
,
?? 2
) , then
a. ?? '
( 0)= -
?? 2
b. ?? '
( ?? ) is not defined at ?? = 0
c. ?? '
( ?? ) is decreasing in ( -
?? 2
, 0) and ?? '
( ?? ) is decreasing in ( 0,
?? 2
)
d. ?? '
( ?? ) is increasing in ( -
?? 2
, 0) and ?? '( ?? ) is increasing in ( 0,
?? 2
)
8
th
January 2020 (Shift 1), Mathematics Page | 4
Answer: ( ?? )
Solution:
?? ( ?? )= ?? cos
-1
( sin ( -|?? |) )
? ?? ( ?? )= ?? cos
-1
( -sin|?? |)
? ?? ( ?? )= ?? [?? - cos
-1
( sin|?? |) ]
? ?? ( ?? )= ?? [?? - (
?? 2
- sin
-1
( sin|?? |) ) ]
? ?? ( ?? )= ?? (
?? 2
+ |?? |)
? ?? ( ?? )= {
?? (
?? 2
+ ?? ), ?? = 0
?? (
?? 2
- ?? ), ?? < 0
? ?? '( ?? )= {
(
?? 2
+ 2?? ), ?? = 0
(
?? 2
- 2?? ), ?? < 0
Therefore, ?? '( ?? ) is decreasing ( -
?? 2
,0) and increasing in ( 0,
?? 2
) .
7. Ellipse 2?? 2
+ ?? 2
= 1 and ?? = ???? meet at a point ?? in the first quadrant. Normal to the
ellipse at ?? meets ?? -axis at ( -
1
3v2
,0) and ?? -axis at ( 0,?? ) , then |?? | is
a.
2
3
b.
2v2
3
c.
v2
3
d.
2
v3
Answer: ( ?? )
Solution:
8
th
January 2020 (Shift 1), Mathematics Page | 5
Let ?? = ( ?? 1
,?? 1
)
2?? 2
+ ?? 2
= 1 is given equation of ellipse.
? 4?? + 2?? ?? '
= 0
? ?? '
|
( ?? 1
,?? 1
)
= -
2?? 1
?? 1
Therefore, slope of normal at ?? ( ?? 1
,?? 1
) is
?? 1
2?? 1
Equation of normal at ?? ( ?? 1
,?? 1
) is
( ?? - ?? 1
)=
?? 1
2?? 1
( ?? - ?? 1
)
It passes through ( -
1
3v2
,0)
? -?? 1
=
?? 1
2?? 1
( -
1
3v2
- ?? 1
)
? ?? 1
=
1
3v2
? ?? 1
=
2v2
3
as ?? lies in first quadrant
Since ( 0, ?? ) lies on the normal of the ellipse at point ?? , hence we get
?? =
?? 1
2
=
v2
3
8. If ?????? is a triangle whose vertices are ?? ( 1, -1) , ?? ( 0,2) , ?? ( ?? '
, ?? ') and area of ??????? is
5, and ?? ( ?? '
, ?? ') lies on 3?? + ?? - 4?? = 0, then
a. ?? = 3 b. ?? = 4
c. ?? = -3 d. ?? = 2
Answer: ( ?? )
Solution:
Area of triangle is
?? =
1
2
|
0 2 1
1 -1 1
?? '
?? '
1
| = ±5
-2( 1- ?? '
)+ ( ?? '
+ ?? '
)= ±10
-2+ 2?? '
+ ?? '
+ ?? '
= ±10
3?? '
+ ?? '
= 12 or 3?? '
+ ?? '
= -8
? ?? = 3 or -2
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