SarkariPYQ

SSC CGL 2021 PYQ — Question 72

SSC CGL - 13 Aug 2021 - Shift 1 • Quantitative Aptitude • Q72

Back to paper

If 8(x + y)3 - 27(x - y)3 = (5y - x)(Ax2 + By2 + Cxy), then what is the value of (A + B - C)?

Show answer & explanation

Correct answer: B

Explanation

The correct answer is option 2 i.e. 36

⇒ 8(x + y)3 - 27(x - y)3 = (5y - x)(Ax2 + By2 + Cxy)

By comparing the coefficient of x3

⇒ 8 - 27 = -A

⇒ A = 19

By comparing the coefficient of y3

⇒ 8 + 27 = 5B

⇒ B = 7

By comparing the coefficient of yx2

⇒ 24 + 81 = 5A - C

⇒ 105 = 95 - C

⇒ C = -10

⇒ A + B - C = 19 + 7 - (-10)

⇒ 36