Question

(b) (5x - 7y)(5x + 7y) – 2(x – 2y)²?​

Answer 1

Step-by-step explanation:

By using identity (x-y)(x+y)= (x²-y²)

((5x)²-(7y)²)-2(x-2y)²

(25x²-49y²)-2(x-2y)²

By using identity (x+y)²= x²+2xy+y²

(25x²-49y²)-2(x²+2×x×(-2y)+(-2y)²

(25x²-49y²)-2(x²+4y+4y²)

(25x²-49y²)(-2x²-8y-8y²)

25x²(-2x²-8y-8y²)-49y²(-2x²-8y-8y²)

-50x⁴-200x²y-200x²y²+98x²y²+392y³+392y⁴

-50x⁴+392y⁴+392y³-200x²y-102x²y²

correct explanation

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