JEE 2023 — Mathematics PYQ
JEE | Mathematics | 2023If y(x) = x^x, x > 0, then y′′(2)−2y′(2) is equal to:
Choose the correct answer:
- A.
4loge2+2
- B.
8loge2−2
- C.
4(loge2)2+2
4(loge2)2−2
Explanation
Solution Given y=xx.
Taking log: logy=xlogx.
Differentiating: y1y′=1+logx⟹y′=xx(1+logx).
At x=2: y′(2)=22(1+log2)=4(1+log2).
Differentiating again:
y′′=y′(1+logx)+y(x1)
y′′=xx(1+logx)2+xx(x1)
At x=2: y′′(2)=4(1+log2)2+4(21)=4(1+log2)2+2.
Now, y′′(2)−2y′(2):
=[4(1+log2)2+2]−[2(4(1+log2))]
=4[1+(log2)2+2log2]+2−8−8log2
=4+4(log2)2+8log2+2−8−8log2
=4(log2)2−2.
Correct Option: (4)
Explanation
Solution Given y=xx.
Taking log: logy=xlogx.
Differentiating: y1y′=1+logx⟹y′=xx(1+logx).
At x=2: y′(2)=22(1+log2)=4(1+log2).
Differentiating again:
y′′=y′(1+logx)+y(x1)
y′′=xx(1+logx)2+xx(x1)
At x=2: y′′(2)=4(1+log2)2+4(21)=4(1+log2)2+2.
Now, y′′(2)−2y′(2):
=[4(1+log2)2+2]−[2(4(1+log2))]
=4[1+(log2)2+2log2]+2−8−8log2
=4+4(log2)2+8log2+2−8−8log2
=4(log2)2−2.
Correct Option: (4)

