Let x,y, and z be real numbers such that x + y + z = 6 and 1x+1y+1z = 2. Find x+yz+y+zx+x+zy.
1x+1y+1z=2x+y+zx+y+z(1x+1y+1z)=216(1+y+zx+1+x+zy+1+x+yz)=23+(y+zx+x+zy+x+yz)=12(y+zx+x+zy+x+yz)=9
.x + y + z = 6 (1)
1/x + 1/y + 1/z = 2 ⇒ [ yz + xz + xy] / xyz = 2 ⇒ [ xy + xz + yz] = 2xyz (2)
x + y y + z x + z
Find ____ + ______ + ______ =
z x y
xy ( x + y) + yz( y + z) + xz ( x + z)
________________________________ =
xyz
xy ( 6 - z) + yz ( 6 - x) + xz ( 6 -y)
______________________________ =
xyz
6xy - xyz + 6yz - xyz + 6xz - xyz
_______________________________ =
xyz
6 [ xy + xz + yz ] - 3 [ xxz ]
_______________________ =
xyz
6 [ 2xyz ] - 3 [xyz]
________________ =
xyz
xyz [ 6*2 - 3 ]
____________ =
xyz
6*2 - 3 =
12 - 3 =
9