Exams › SSC CGL (Prelims) › General

Given that x^2 - 2xy = 84 and x - y = -10, find the value of y.

1. 2
2. 1
3. 4
4. 3

Correct answer: 4

Solution

From x - y = -10: x = y - 10. Substituting: (y-10)^2 - 2(y-10)y = 84 => y^2 - 20y + 100 - 2y^2 + 20y = 84 => -y^2 + 100 = 84 => y^2 = 16 => y = 4 (taking positive value). Verification: x = -6, x^2 - 2xy = 36 + 48 = 84. Correct.

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