Question

xy +yz+zx when x+y+z=9 and x²+y²+z²=81​

Answer 1

solution

(x+y+z)²=x²+y²+z²+2(xy +yz+zx)

=>9²=81+2(xy +yz+zx)

=>2(xy +yz+zx)=81-81=0

=>xy +yz+zx=0

Answer 2

Step-by-step explanation:

solution

(x+y+z)²=x²+y²+z²+2(xy +yz+zx)

=>9²=81+2(xy +yz+zx)

=>2(xy +yz+zx)=81-81=0

=>xy +yz+zx=00