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)#