Question 388163
Factor out the 5 first.
{{{x=5y^2+40y+77}}}
{{{x=5(y^2+8y)+77}}}
{{{x=5(y^2+8y+16)+77-5(16)}}}
{{{x=5(y+4)^2+77-90}}}
{{{highlight(x=5(y+4)^2-3)}}}