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SSC CGL 2020 PYQ — Question 59

SSC CGL - 3rd March 2020 Shift 2 • Quantitative Aptitude • Q59

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The expression (a + b - c)3 + (a - b + c)3 - 8a3 is equal to:

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Correct answer: A

Explanation

The correct answer is option 1 i.e 6a(a − b + c)(c − a − b)

Let (a + b - c) = A, (a - b + c) = B and -2a = C

(a + b - c)3 + (a - b + c)3 - 8a3

= A3 + B3 - C3

(a3 + b3 + c3 = 3abc when a + b + c = 0)

so,

= 3ABC

= 3(a + b - c)(a - b + c) × (-2a)

= 6a3(a + b - c)(c - a - b)