Question 1009335


{{{ x^2-7x}}}.......recall:{{{(a-b)^2=a^2-2ab+b^2}}}; so, to make it  perfect square we need to add {{{b^2}}}

{{{ x^2-7x+b^2}}}...when you compare it to {{{a^2-2ab+b^2}}}, you see that {{{a=1}}} and {{{2ab=7}}}

now we can find {{{b}}}:

{{{2ab=7}}}=>{{{2*1*b=7}}}=>{{{b=7/2}}}

then we have:

{{{ x^2-7x+(7/2)^2}}}

{{{ (x-7/2)^2}}}