Q.

Let a differentiable function f satisfy the equation 036f(tx36)dt=4αf(x). If y=f(x) is a standard parabola passing through the points (2, 1) and (-4,β), then βα is equal to _____.                [2026]


Ans.

(64)

036f(tx36)dt=4αf(x),   Put tx36=y

                                                      dydt=x36

0xf(y)36dyx=4αf(x)

0xf(y)dy=αf(x)x9

f(x)=α9(f(x)+xf'(x))

(1-α9)f(x)=αx9f'(x)(9-α)f(x)=αxf'(x)

f'(x)f(x)=(9α-1)1x

logef(x)=(9α-1)logex+logec

f(x)=cx(9α-1) For standard parabola,

9α-1=2

α=3

f(x)=cx2

Passing through (2,1)

1=4cc=14

y=x24  passing through (-4,β)

β=4

βx=43=64