Question

if X + Y is equal to 8 and x y equal to 15 then find the value of x square + Y square

Answer 1

$x + y = 8 \: xy = 15 \: x { }^{2} + y {}^{2} =120 - 64 = 56$

Answer 2

x+y=8
xy=15
y=8-x
x(8-x)=15
8x-x2=15
x2-8x+15=0
x=5,3
Sub x in y
y=5,3
X2+y2=(5)2+(3)2=34
X2+y2=(3)2+(5)2=34