Real numbers x and y have a difference of 16 and a product of 23. Find x^2+y^2.
x - y = 23
Square both sides
x^2 - 2xy + y^2 = 529 (1)
xy = 23
2xy = 46 (2)
Sub (2) into (1)
x^2 -2(46) + y^2 = 529
x^2 - 92 + y^2 = 529 add 92 to both sides
x^2 + y^2 = 621
+223 
