Differential EquationHard

Question

A function f(x) satisfying f (tx)dt = nf (x), where x > 0, is -

Options

A.f (x) = c.x1-n/n
B.f (x) = c.xn/1-n
C.f (x) = c.x1/n
D.f (x) = c.x(1-n)

Solution

f(tx)dt = nf(x)
Let tx = u ⇒ dt =
f(u)du = nf (x) ⇒ f(u)du = nxf (x)
f (x) = n[f (x) + xf′(x)] ⇒ f(x) = xf′(x)
lnx = lny + lnc
x1-n/n = cy ⇒ y = c′x1-n/n

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