Question 42925
First, look at the standard equation: {{{ax^2 + bx + c}}}
You need to find factors of {{{ac}}} that sum up to {{{b}}}
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{{{b^2 + 18b + 81}}} sum of factors of {{{81}}} to get {{{18}}}? -> 9 + 9
{{{b^2 + 9b + 9b + 81}}}
{{{(b^2 + 9b) + (9b + 81)}}}
{{{b(b + 9) + 9(b + 9)}}}
{{{(b + 9)(b + 9)}}}
{{{(b + 9)^2}}}