Precalculus (6th Edition)

(a) This is a perfect square trinomial since it is in the form $a^2+2ab+b^2$ where $a=x$ and $b=5y$. Thus, its factored form is $(x+5y)^2$ so the answer is B. (b) This is a perfect square trinomial since it is in the form $a^2-2ab+b^2$ where $a=x$ and $b=5y$. Thus, its factored form is $(x-5y)^2$ so the answer is C. (c) This is a difference of two squares since it is in the form $a^2-b^2$ where $a=x$ and $b=5y$. Thus, its factored form is $(x-5y)(x+5y)$ so the answer is A. (d) This is a difference of two squares since it is in the form $a^2-b^2$ where $a=5y$ and $b=x$. Thus, its factored form is $(5y-x)(5y+x)$ so the answer is D.