Question by Lionel Messi - Discuss with MathYouLike

Lionel Messi

19/03/2017 at 11:52

Suppose (x+y)² = 18 and (x-y)² = 12. Find the value of x² + y².

Operation of Indices

List of answers

FA KAKALOTS 06/02/2018 at 12:29

We have : (x + y)2 - (x - y)2 = 18 - 12

(x2 + 2xy + y2) - (x2 - 2xy + y2) = 6

4xy = 6

2xy = 3

=> x2 + y2 = 18 - 3 = 15
Phan Thanh Tinh Coordinator 23/03/2017 at 17:45

We have : (x + y)² - (x - y)² = 18 - 12

(x² + 2xy + y²) - (x² - 2xy + y²) = 6

4xy = 6

2xy = 3

=> x² + y² = 18 - 3 = 15

Weekly ranking