How do you factor $9 x^{2} - 121$ $9x^2-121$ ?

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Answer 1 · 2015-05-01T17:23:49

Note that $9 x^{2} = {(3 x)}^{2}$ $9x^2 = (3x)^2$
and
$121 = 11^{2}$ $121 = 11^2$

So
$9 x^{2} - 121$ $9x^2 -121$ is the difference of two squares.

In its general form the difference of two squares:
$(a^{2} - b^{2}) = (a + b) (a - b)$ $(a^2-b^2) = (a+b)(a-b)$

So
$9 x^{2} - 121$ $9x^2-121$
$= {(3 x)}^{2} - 11^{2}$ $= (3x)^2-11^2$
$= (3 x + 11) (3 x - 11)$ $= (3x+11)(3x-11)$

How do you factor 9x2−1219x^2-121?