Question

x+y+z=10 and x^2+y^2+z^2=40 find xy+yz+zx

Answer 1

(x+y+z)²=x²+y²+z²+2(xy+yz+zx)
100=40+2(xy+yz+zx)
60/2=xy+zx+yz
30=xy+yz+zx

Answer 2

Hey ananya
your answer is here
as we know that (x+y+z)^2 = x^2+y^2+z^+2(xy+yz+xz)

by putting the value

100 = 40 + 2(xy+yz+zx)

Hence
xy+yz+zx = 30

Thanks

Be Brainy