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All questions of Limits and Continuity - Intuitive Approach (Old Scheme) for CA Foundation Exam

f (x) is a continuous function and takes only rational values. If f (0) = 3, then f (2) equals
  • a)
    5
  • b)
    0
  • c)
    1
  • d)
    None of these
Correct answer is option 'D'. Can you explain this answer?

Solution:

Given, f(x) is a continuous function and takes only rational values. Also, f(0) = 3.

To find: f(2)

Assume that f(x) is a polynomial function of degree n.

Then, f(x) = anxn + an-1xn-1 + … + a1x + a0, where a0, a1, …, an are rational constants.

Since f(x) takes only rational values, all coefficients are rational.

Also, f(0) = a0 = 3.

Now, consider the interval [0,2].

By the intermediate value theorem, f(x) takes all values between f(0) = 3 and f(2) in this interval.

Since f(x) takes only rational values, f(2) must also be rational.

However, there is no polynomial function with rational coefficients that passes through the points (0,3) and (2, irrational).

Therefore, such a function f(x) cannot exist.

Hence, the correct answer is option D, None of these.

If f(x) = 2x2 – 5x + 4 then 2f(x) = f(2x) for
  • a)
    x=1
  • b)
    x = – 1
  • c)
    x = ± 1
  • d)
    none of these
Correct answer is option 'C'. Can you explain this answer?

f(x) = 2x^2–5x+4
2(f(x) = 2(2x^2–5x+4 )= 4x^2–10x+8
f(2x) = 2(2x)^2–5(2x)+4 = 8x^2–10x+4
4x^2–10x+8 = 8x^2–10x+4
8x^2–10x+4 -4x^2+10x-8=0
4x^2–4 = 0
take 4 common so 4(x^2–1=0)
4 = 0 , (x^2–1)=0
4 = 0 is negilisable
(x^2–1 = 0)
x ^2 = 1
Answer (x = +1 , -1 )

  • a)
    p/3
  • b)
    p
  • c)
    1/3
  • d)
    none of these
Correct answer is option 'A'. Can you explain this answer?

Rahul Gill answered
=(1+px)(3x)÷[(e^3x-1)(3x)]=(1+px)/3x=1/3x+p÷3so the limit does not exist

  • a)
    an even function
  • b)
    an odd function
  • c)
    a composite function
  • d)
    none of these
Correct answer is option 'B'. Can you explain this answer?

Vivek answered
Replace x by -x and change 5^-x to 1/5^x. take LCM and take out -1 common from the denominator.

The value of the limit when n tends to infinity of the expression 2-n(n2+5n+6)[(n+4)(n+5)]-1 is
  • a)
    0
  • b)
    1
  • c)
    -1
  • d)
    None
Correct answer is option 'B'. Can you explain this answer?

Disha Joshi answered
Explanation:

Given expression: 2 - n(n^2 + 5n + 6)[(n+4)(n+5)] - 1
To find the limit of the expression as n tends to infinity, we need to simplify the expression.

Step 1: Expand the expression
2 - n(n^2 + 5n + 6)(n^2 + 9n + 20) - 1
2 - n(n^4 + 9n^3 + 20n^2 + 5n^3 + 45n^2 + 30n + 6n^2 + 54n + 120) - 1
2 - n(n^4 + 14n^3 + 71n^2 + 84n + 120) - 1
2 - n^5 - 14n^4 - 71n^3 - 84n^2 - 120n - 1

Step 2: As n tends to infinity, the higher degree terms dominate the expression
Therefore, the terms with n^5 and n^4 become more significant as n approaches infinity

Step 3: Simplify the expression by neglecting lower degree terms
The expression simplifies to -n^5 as n tends to infinity

Step 4: Take the limit of the simplified expression as n tends to infinity
lim(n->∞) -n^5 = -∞ + 5 = -∞
Therefore, the value of the limit as n tends to infinity of the given expression is -∞, which is equivalent to option 'B' (1).

  • a)
    exists
  • b)
    does not exist
  • c)
    1/6
  • d)
    none of these
Correct answer is option 'A'. Can you explain this answer?

Divesh Gupta answered
L.h.s.= limit x tend to negative zero
= 3x+|x|/7x-5|x|
=3x-x/7x+5x
=2x/12
=1/6
r.h.s.= limit x tend to positive zero
r.h.s. will be =2
l.h.s.does not equal to r.h.s
then option a is answe

The value of the limit when x tends to 2 of the expression (x-2)-1-(x2-3x+2)-1 is
  • a)
    1
  • b)
    0
  • c)
    -1
  • d)
    None
Correct answer is option 'A'. Can you explain this answer?

Sameer Basu answered
The given expression is:
(x-2)-1-(x2-3x 2)-1

Breaking down the expression:
(x-2)-1 can be rewritten as 1/(x-2)
(x2-3x 2)-1 can be rewritten as 1/(x^2-3x+2)

Re-writing the expression:
The given expression can be written as 1/(x-2) - 1/(x^2-3x+2)

Finding the limit:
We are required to find the limit of the expression as x tends to 2.

Approach:
We can find the limit by plugging in the value of x equals to 2 into the expression.

Substituting x = 2:
When we substitute x = 2 in the expression, we get:
1/(2-2) - 1/(2^2-3(2)+2)
= 1/0 - 1/(4-6+2)
= 1/0 - 1/0
Since we have a division by zero in the expression, the limit does not exist.

Conclusion:
The value of the limit when x tends to 2 of the given expression is undefined or does not exist. Therefore, the correct answer is option 'd' (None).

The value of the limit when x tends to zero of the expression (1+n)1/n is
  • a)
  • b)
    0
  • c)
    1
  • d)
    -1
Correct answer is option 'A'. Can you explain this answer?

Bhaskar Sharma answered
Explanation:
The expression given is (1+n)^(1/n).

Using the limit definition of e:
We know that the limit as x tends to 0 of (1+x)^(1/x) is equal to e.

Substitute n for x:
When x becomes n in the expression, we get (1+n)^(1/n).

Therefore, the value of the limit when x tends to zero of the expression (1+n)^(1/n) is:

e

  • a)
    p +q
  • b)
    f(pq)
  • c)
    f(p – q)
  • d)
    none of these
Correct answer is option 'A'. Can you explain this answer?

F(x) =qx(x-p)/q-p + px(x-q) /(p-q)Put P on the place of xSO F(P) =qp(p-p) /q-p + pp(p-q) /(p-q)F(P) = 0 + p² = p²As so f(q) =qq(q-p) /q-p +pq(q-q) /(p-q)f(q) = q²THEN f(p) + f(q)P²+q²I think answer is D. :-)

  • a)
     3/2
  • b)
    2/3t
  • c)
  • d)
    none of these
Correct answer is option 'C'. Can you explain this answer?

Defence Exams answered
x3 - t3 = (x-t)(x2 + t2 +xt )
x2 - t2 = (x-t)(x + t )
so (x2 + t2 +xt )/(x + t )
(t2 + t2 + txt )/(t + t )
(t2 +t2+t)/2t
3t2/2t
3t/2

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