1.(2x^2-4)(2x^2+4) 2.(5yz+6x^2)(5yz-6x^2) 3.(x^2+y^2)(x^2-y^2)
(a-b)(a+b) = a^2-b^2 So, #1: (2x^2)^2 - 4^2 = 4x^4 - 16 now try the others.
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