Question 1069008
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The last term is 81:


x^2-18x + 81 = {{{(x-9)^2}}}.


Having the term "-18x", you can easily understand that it is "-2*9*x", hence, {{{9^2}}} = 81 is the last (third term) they are asking for.



MEMORIZE these identities:  {{{x^2 + 2bx + b^2}}} = {{{(x+b)^2}}},

                            {{{x^2 - 2bx + b^2}}} = {{{(x-b)^2}}}.
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