Stuck on Khan Academy Math Problem: Structure in Expressions

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I am having trouble understanding a math problem on Khan Academy even with the explanation they give me.

The expression: $$({x^2} + {h^2})({x^2} - {h^2}) $$ can be written as $$(1 + m - p){x^4} - mp $$ where h, m, and p are constants what is one possible value of m?

The answer is $${h^2} $$

I don't understand how they got that. I know that:$$\begin{array}{l}({x^2} + {h^2})({x^2} - {h^2}) = ({x^4} - {h^4})\\\end{array} $$

But when I set equal both equations I get $$\begin{array}{l}\frac{{({x^4} - {h^4}) = (1 + m - p){x^4} - mp}}{{{x^4}}} = \\1 - {h^4} = 1 + m - p - mp = \\ - {h^4} = m - p - mp = \\m = {h^4} - p - mp\end{array} $$ The answer I got was different from the answer KhanAcademy got.

Can one explain how $h^2$ is the answer and why the answer I got is incorrect.

Thank you so much!

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I think it must be $$1+m-p=1$$ and $$mp=h^4$$ solving this we get $$m=\pm h^2$$ and $$p=\pm h^2$$