Mathematics

Problem

Consider the integral

\int x^{3}\sqrt{1 - x^{4}}\,dx.

Which substitution will MOST directly transform the integrand into a simple power of the new variable that can be integrated in a single step? a)

u = x^{4}

u = 1 - x^{2}

u = 1 - x^{4}

u = \sqrt{1 - x^{4}}