If f(x)=asin(logx) prove that x^2f"(x)+f'+f(x)=0

We have,Let y = fx.Then,y = a sin log xdydx = a coslog x × 1xd2ydx2 = acoslog x × -1x2 +1x × - sin log x  × 1xd2ydx2 =-ax2coslog x +sin log xNow,LHS = x2d2ydx2 + xdydx + y=-acoslog x +sin log x + a coslog x +  a sin log x=0=RHS

  • 1

f(x) = aSin(Logx)

Differentiating the equation with respect to x:-

f'(x) = a.[ Cos(Logx) ] * (1/x)

x.f'(x) = aCos(Logx)

Differentiating again with respect to x:-

1.f'(x) + x.f''(x) = { a[-Sin(Logx)] } * (1/x)

.

x.f'(x) + (x^2).f''(x) = -aSin(Logx)

.

x.f'(x) + (x^2).f''(x) + aSin(Logx) = 0

.

Here, aSin(Logx)= f(x).

Therefore,

x.f'(x) + (x^2).f''(x) + f(x) = 0

.

Hence proved.

.

  • 0
What are you looking for?