# Math Help - Change of Variables

1. ## Change of Variables

Tricky....

Reduce u'' + (ax+b)u = 0 to u'' + tu = 0 by a suitable change of variables.

2. Let ax+b = t, then by differenciating u(x) with respect to t twice using the chain rule you will get (a^2)u'' + tu = 0. Is this what you wanted?

3. this can surely not be the whole story, since by just chosing $t=ax+b$ your problem will already be solved...

$\frac{d^{2}u(x)}{dx^{2}}+(ax+b)u(x)=0$
$\frac{d^{2}u(z)}{dz^{2}}+tu(z)=0$