Cevap:
[tex] {(x + y)}^{2} = {x}^{2} + {y}^{2} + 2xy \\ {(12)}^{2} = 86 + 2xy \\ 144 = 86 + 2xy \\ 144 - 86 = 2xy \\ 58 = 2xy \\ xy = 29[/tex]
