Question

Si x2+y2=82; x+y=10. Calcular xy

Answer 1

x²₊y²=82;x₊y=10

Ahora

x₊y=10

Lo elebamos al cuadrado

(x₊y)²=10²

x²₊2xy₊y²=100
(x²₊y²)₊2xy=100
(82)₊2xy=100
2xy=100-82
2xy=18
  xy=18/2
  xy=9

Rpta: xy=9