# Chapter P, Prerequisites - Chapter P Review - Exercises - Page 77: 64

$3(y-3x)(y^2+3xy+9x^2)$

#### Work Step by Step

Factor out the GCF (which is $3$) to obtain: $=3(y^3-27x^3)$ Since $27=3^3$, the expression above is equivalent to: $=3(y^3-3^3x^3) \\=3[y^3-(3x)^3]$ The second factor in the expression above is a difference of two cubes. Factor using the formula $a^3-b^3=(a-b)(a^2+ab+b^2)$ with $a=y$ and $b=3x$ to obtain: $=3(y-3x)[y^2+y(3x) + (3x)^2] \\=3(y-3x)(y^2+3xy+9x^2)$

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