Question

If x+y=15 and x-y=25, then what is the value of 2x^2 - y^2?

A) 425
B) 775
C) 825
D) 1,575
E) 1,625 ...?

Answer 1

I suggest you to use this fromula to solve it: (x−y)(x+y)=x^2−y^2. I'll help you by telling what the values of x and y. y= -5, x = 20. Just put it there and you'll get the answer.