Question

If x -y = 5 and xy= 14 find the value of x square- y square??????

Answer 1

x-y=5
x=5+y

xy=14
y(5+y)=14
5y+y^2-14=0
y^2+7y-2y-14=0
y(y+7)-2(y+7)=0
(y-2)(y+7)=0
y=2,-7


x-(-7)=5 or x-2=5
x=-2,7
now you can find
x^2-y^2