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'Scale Invariance' printed from https://nrich.maths.org/
Don't forget that probability distribution functions must integrate
to $1$ over the allowed range of values.
Try changing variables for the first part.
For the second part, note that clearly $x^2\rightarrow (ax)^2 \neq
a(x^2).$
How could you make the two sides match for other powers of
$x$?