Answer
$16x^4-625$
Work Step by Step
$$(2x+5)(2x-5)(4x^2+25)$$ To multiply the sum of two terms by the difference of two terms, use the formula: $(a+b)(a-b)=a^2-b^2$: $$=[(2x)^2-(5)^2](4x^2+25)$$ $$=(4x^2-25)(4x^2+25)$$ This is also the product of the sum of two terms by the difference of two terms!: $$=(4x^2)^2-(25)^2$$ $$=16x^4-625$$
