NIMCET 2026 — Mathematics PYQ
NIMCET | Mathematics | 2026Let f:[0,∞)→R be a function defined by f(x)=x2+3x+23x2+4x+1. Then the value of (f−1)′(2) is equal to:
Choose the correct answer:
- A.
5
(Correct Answer) - B.
25
- C.
15
- D.
0
5
Explanation
The derivative of the inverse function is given by the formula:
(f−1)′(y)=f′(x)1, where f(x)=y
1. Find x such that f(x)=2:
x2+3x+23x2+4x+1=2
3x2+4x+1=2(x2+3x+2)
3x2+4x+1=2x2+6x+4
x2−2x−3=0
(x−3)(x+1)=0
Since the domain is [0,∞), we have x=3.
2. Find f′(x):
Using the quotient rule (vu)′=v2u′v−uv′:
u=3x2+4x+1⟹u′=6x+4
v=x2+3x+2⟹v′=2x+3
f′(x)=(x2+3x+2)2(6x+4)(x2+3x+2)−(3x2+4x+1)(2x+3)
3. Evaluate f′(3):
At x=3:
u=3(9)+4(3)+1=40
u′=6(3)+4=22
v=32+3(3)+2=20
v′=2(3)+3=9
f′(3)=(20)2(22)(20)−(40)(9)=400440−360=40080=51
4. Calculate (f−1)′(2):
(f−1)′(2)=f′(3)1=1/51=5
Correct Option: (b)
Explanation
The derivative of the inverse function is given by the formula:
(f−1)′(y)=f′(x)1, where f(x)=y
1. Find x such that f(x)=2:
x2+3x+23x2+4x+1=2
3x2+4x+1=2(x2+3x+2)
3x2+4x+1=2x2+6x+4
x2−2x−3=0
(x−3)(x+1)=0
Since the domain is [0,∞), we have x=3.
2. Find f′(x):
Using the quotient rule (vu)′=v2u′v−uv′:
u=3x2+4x+1⟹u′=6x+4
v=x2+3x+2⟹v′=2x+3
f′(x)=(x2+3x+2)2(6x+4)(x2+3x+2)−(3x2+4x+1)(2x+3)
3. Evaluate f′(3):
At x=3:
u=3(9)+4(3)+1=40
u′=6(3)+4=22
v=32+3(3)+2=20
v′=2(3)+3=9
f′(3)=(20)2(22)(20)−(40)(9)=400440−360=40080=51
4. Calculate (f−1)′(2):
(f−1)′(2)=f′(3)1=1/51=5
Correct Option: (b)
