Question

If x + y = 8 and xy =15 , find x2 + y2.

Answer 1

Here is your answer

$x {}^{2} + y {}^{2} = (x + y) {}^{2} - 2xy \\ x {}^{2} + y {}^{2} = 8 {}^{2} - 2(15) \\ x {}^{2} + y {}^{2} = 64 - 30 \\ x {}^{2} + y {}^{2} = 34$
Hope it helps you

Answer 2

X2 +y2=(x+y)2-2xy

8^2×2+2×15

64×2+2×15

128+30

158