Question 960249

{{{y=x^2-4x-10 }}}...first group first two terms

{{{y=(x^2-4x)-10 }}} ...add some number squared in parentheses and deduct it after

{{{y=(x^2-4x+b^2)-b^2-10 }}}....recall the rule:{{{(a-b)^2=a^2-2ab+b^2}}}

compare to {{{(x^2-4x+b^2)}}} and you can see that {{{a=1}}} and {{{2ab=4}}}=>

{{{2*1b=4}}}
{{{2b=4}}}
{{{b=4/2}}}
{{{b=2}}}....now add it to your equation {{{y=(x^2-4x+b^2)-b^2-10 }}}

{{{y=(x^2-4x+2^2)-2^2-10 }}}

{{{y=(x-2)^2-4-10 }}}

{{{y=(x-2)^2-14 }}}