How do you factor $x^2+18x+81$ ?

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Answer 1 · 2016-06-01T12:16:17

$x^2+18x+81=(x+9)^2$

As $81$ is the square of $9$ and middle term $18$ is double of this number, (compare it with $(x+a)^2=x^2+2ax+a^2$ )

Hence $x^2+18x+81$ is a complete square.

$x^2+18x+81$

= $x^2+2xx9xx x+9^2$

= $(x+9)^2$

How do you factor x^2+18x+81x^2+18x+81?