If x2 - 2xy = 84 and x - y = -10, then the value of y is:
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 4.
We have been given in the question,
x2 - 2xy = 84....(1)
⇒ x - y = -10
⇒ x = y - 10
Put the value of x in equation 1.
(y - 10)2 - 2(y - 10)y = 84
⇒ y2 + 100 - 20y - 2y2 + 20y = 84
⇒ -y2 = -16
⇒ y = 4