Question

If x+y+z=9 and x2+y2+z2=29 then xy + yz + xz equals to

Answer 1

Answer:

Step-by-step explanation:

(x+y+z)² = x² + y² + z² +2(xy + yz + zx)

9² = 29 +2(xy + yz + zx)

2(xy + yz + zx) =52

xy + yz + zx = 52/2 = 26.

Answer 2

Answer:

26

Step-by-step explanation:

x+y+z=9

(x+y+z)²=81

x²+y²+z²+2xy+2yz+2zx=81

29+2xy+2yz+2zx=81. (x²+y²+z²=29)

2xy+2yz+2zx=81-29

2(xy+yz+zx)=52

xy+yz+zx=26