2022 · Q61
If x is the harmonic mean between y and z, then which one of the following is correct?
Elementary MathematicsAlgebra
- Axy + xz - yz = 0
- Bxy + xz - 2yz = 0
- Cxy + xz + yz = 0
- Dxy + xz - 4yz = 0
Explanation
x is the harmonic mean of y and z: x = 2yz/(y+z), so x(y+z) = 2yz, i.e. xy+xz−2yz = 0. The keyed option is B.