Question

If x-y =7and x² +y²=85 find the value of x³-y cube​

Answer 1

Given ,

=> X - Y = 7

=> X³ - Y³ =133

To Find

=> x² + y² = ????

Applying Formula ----

=> (X - Y)³ = X³ - Y³ - 3XY(X-Y)

=> (7)³ = 133 - 3XY(7)

=> 343 -133 = - 21X.Y

=> -210 = 21X.Y

=> X.Y = -10

NOW :-

=> (X - Y)² = X² + Y² -2X.Y

=> 49 = X² + Y² -(-20)

=> X² + Y² => 49 -20

=> X² + Y² = 29

By this u can get the answer.

I think u Understand the answer.