Question 851991
You are supposed to SUBSTITUTE what you are told to substitute.  Just do that.

You must obtain {{{highlight(y=16x^4+6x^2+4)}}} when you are finished.


After feedback, the first step needs to be clarified.
{{{4u^2 + 3u + 4}}} and {{{u = 2x^2}}}
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Make the substitution.
{{{4(2x^2)^2+3(2x^2)+4}}}
and ONE MORE step.
{{{4(2*2*x^2*x^2)+3*2*x^2+4}}}