Question

If x+y+z=15, xy+yz+zx=15 then find the value of x square+ y square + z square

Answer 1

(x + y + z)² = x² + y² + z² + 2(ab+ac+ bc)

15² = x² + y² + z² + 2 x15

225 = x² + y² + z² + 30

x² + y² + z² = 225 - 30 = 195