Question 908275
Let's simplify.
{{{(a-b)(a+b)=(a-b)a+(a-b)b}}}
{{{(a-b)(a+b)=a^2-ab+ab-b^2}}}
{{{(a-b)(a+b)=a^2-b^2}}}
So then,
{{{((2/5)x-(3/4)y^2)((2/5)x+(3/4)y^2)=((2/5)x)^2-((3/4)y^2)^2}}}
{{{((2/5)x-(3/4)y^2)((2/5)x+(3/4)y^2)=highlight((4/25)x^2-(9/16)y^4)}}}