Question 1117089
{{{x^2 + 2x + blank}}}

recall: 

{{{(a+b)^2=a^2+2ab+b^2}}}...so, your {{{blank}}} is {{{b^2}}}

use given coefficients {{{a=1}}} and  {{{2ab=2}}} and find {{{b}}}

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

so, {{{blank=1^2}}}

{{{x^2 + 2x + 1^2}}}->{{{x^2 + 2x + 1}}}->{{{(x+1)^2}}}