Question 318555
To complete take (1/2) of the x-coefficient, square it.
That's added to the left hand side.
(1/2) of the x-coefficient is added to the right hand side.
{{{x^2+16x+b^2=(x+b)^2}}}
{{{x^2+16x+b^2=x^2+2bx+b^2}}}
{{{16x=2bx}}}
{{{b=16/2=8}}}
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{{{x^2+16x+64=(x+8)^2}}}