Question 574633
take 1/2 of the coefficient of {{{x}}},
square it, and add to expression
{{{x ^2 + 10x + (10/2)^2 }}}
{{{ x^2 + 10x + 25 }}}
{{{ ( x + 5 )^2 }}}
25 must be added to each binomial expression 
to form a perfect-square trinomial.