Question

2
If x²- y² = 20 and x+y = 10, then find x

Answer 1

x = 6

Explanation:

x² - y² is a difference of squares and factors as (x + y)(x - y)

given

x² - y² = 20 , then

(x + y)(x - y) = 20 ← substitute x + y = 10

10(x - y) = 20 ( divide both sides by 10 )

x - y = 2 → (1)

x + y = 10 → (2)

add (1) and (2) term by term to eliminate y

2x + 0 = 12

2x = 12 ( divide both sides by 2 )

x = 6