Which expression is equivalent to x^4 - 12x^2 + 36?
(1) (x^2 - 6)(^x2 - 6) (3) (6 - x^2)(6 + x^2)
(2) (x^2 + 6)(x^2 + 6) (4) (x^2 + 6)(x^2 - 6)

So the answer is
(x^2 plus or minus 6)(x^2 plus or minus 6)
an easy way to do this is to only look at plus or minus 6
x^4 - 12x^2 + 36   (-12 and 36)

6 x 6 = 36
6 + 6 ≠ -12              (x^2 + 6)(x^2 + 6) is incorrect        

6 x -6 ≠ 36
6 + -6 ≠ -12             (x^2 - 6)(x^2 + 6) is incorrect

-6 x -6 = 36
-6 + -6 = -12         (x^2 - 6)(x^2 - 6) is correct

the answer is (1)

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