Question

Use polynomial identities to multiply (5 - 4x3)(5 + 4x3). What identity did you use?

Answer 1

$\textit{difference of squares} \\\\ (a-b)(a+b) = a^2-b^2 \\\\[-0.35em] ~\dotfill\\\\ (5-4x^3)(5+4x^3)\implies [(5)^2-(4x^3)^2]\implies [(5^2)-(4^2x^{3\cdot 2})] \\\\[-0.35em] ~\dotfill\\\\ ~\hfill 25-16x^6~\hfill$