Given that (x+y+z)(xy+xz+yz)=25 and that x^2(y+z)+y^2(x+z)+z^2(x+y)=7 for real numbers x, y, and z, what is the value of xyz?
You are given that (x + y + z)(xy + xz + yz) = 25
Expanding the left side of (x + y + z)(xy + xz + yz) = 25
you get: x2y + x2z + y2x + y2z + z2x + z2y + 3xyz = 25
Factoring this, you get: x2(y + z) + y2(x + z) + z2(x + y) + 3xy = 25
Since you know that x2(y + z) + y2(x + z) + z2(x + y) = 7
Subtracting down: 3xyz = 18
Dividing by 3: xyz = 6