Question

If x^2 - y^2 = 36 and x + y = 9, what is the value of x -y?

Answer 1

x-y = 4

Explanation:

1. evaluate x² and y².

x²-y² = 36.

x+y+9.

2. subsitute.

36 = 9(x-y)

3. rearrange terms.

9(x-y) = 36.

divide both sides and simplify.

Answer 2

x - y = 4

Explanation:

Use the identity

(x + y) (x -y) = x² - y²

Plugging in knowns
(x-y) 9 = 36

Divide both sides by 9 to get

x - y = 36/9 = 4

So x - y = 4