How do you multiply $(x3a - 3)(x3a + 3)$ ?

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Answer 1 · 2017-06-04T18:02:50

See a solution process below:

This is a special form of the quadratic equation:

$(a - b)(a + b) = a^2 - b^2$

Let $a = x3a$ and let $b = 3$ and substitute to get:

$(x3a - 3)(x3a + 3) = (x3a)^2 - 3^2 = x^23^2a^2 - 9 =$

$9x^2a^2 - 9$

Or

$9(x^2a^2 - 1)$

How do you multiply (x3a - 3)(x3a + 3)(x3a - 3)(x3a + 3)?