Question

(x-y)^2= 16 xy= -6 What is (x+y)^2?

Answer 1

`(x+y)^2=-8`

Explanation:

As `(x+y)^2=x^2+y^2+2xy` and `(x-y)^2=x^2+y^2-2xy`

`(x+y)^2-(x-y)^2=4xy` (A)

Now as `(x-y)^2=16` and `xy=-6`, putting these in (A), we get

`(x+y)^2-16=4xx(-6)`

or `(x+y)^2=-24+16=-8`