Question

Expand by using suitable identity (3 a - 7 b - c)^2
i dentity is (x-y-z)^2​

Answer 1

Here the identity used is (x+y+z)².

where x=3a, y=-7b, z=-c

(x+y+z)²= x²+y²+z²+2xy+2yz+2zx

(3a)²+(-7b)²+(-c)²+2*3a*-7b+2*-7b*-c+2*-c*3a

9a²+49b²+c²-42ab+14bc-6ac is ur answer.

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