Question 894316
{{{(x-y)^2=x^2-2xy+y^2}}}
So then,
{{{(x-y)^2+5xy=x^2-2xy+y^2+5xy}}}
{{{(x-y)^2+5xy=x^2+3xy+y^2}}}
Substituting,
{{{x^2+3xy+y^2=7^2+5(-8)}}}
{{{x^2+3xy+y^2=49-40}}}
{{{x^2+3xy+y^2=9}}}