Question

Which products result in a difference of squares? Check all that apply. (x – y)(y – x) (6 – y)(6 – y) (3 + xz)(–3 + xz) (y2 – xy)(y2 + xy) (25x – 7y)(–7y + 25x) (64y2 + x2)(–x2 + 64y2)

Answer 1

difference of squares formula:
a^2 – b^2 = (a + b)(a – b)

so answers are

(3 + xz)(–3 + xz)
(y2 – xy)(y2 + xy)
(64y2 + x2)(–x2 + 64y2)


cause
(3 + xz)(–3 + xz)
= (xz + 3 )(xz - 3)
= x^2z^2 - 9

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(y^2 – xy)(y^2 + xy)
= y^4 -x^2y^2

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(64y^2 + x^2)(–x2 + 64y^2)
=(64y^2 + x2)(64 - x^2)
= 64^2 y^4 - x^4