Question

25a²-4b²+28 bc - 490²​

Answer 1

Step-by-step explanation:

5a²)-(2b)²-28bc-(7c)²

(5a²)-{(2b)²+28bc+(7c)²}

(5a²)-{(2b)²+2×2b×7c+(7c)²}

(5a²)-(2b+7c)² [(x+y)²=x²+2xy+y²]

{(5a²)-(2b+7c)²} {(5a²)+(2b+7c)²} [x²-y²=(x-y) (x+y)

= (5a-2b-7c) (5a+2b+7c)

 hence proved

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