1. Given x ^ 2 + xy = 10, y (x + y) = 15, then x + y =? 2, if (a-b) ^ 2-2a + 2B + 1 = 0, then A-B =? 2?

1. Given x ^ 2 + xy = 10, y (x + y) = 15, then x + y =? 2, if (a-b) ^ 2-2a + 2B + 1 = 0, then A-B =? 2?

x^2+xy=10(1)
y(x+y)=15(2)
(1) (2) x / y = 2 / 3
(2) (1) y ^ 2-x ^ 2 = 5
We get x = 2, y = 3 or x = - 2, y = - 3
X + y = 5 or - 5
(a-b)^2-2a+2b+1=0
We get (a-b) ^ 2-2 (a-b) + 1 = 0
We get (a-b-1) ^ 2 = 0
We get A-B = 1