Chapter 7.2, Problem 34E

To determine

To prove:That $f\left(a,b\right)=a.\left[\frac{\partial f}{\partial x}\left(a,b\right)\right]+b\cdot \left[\frac{\partial f}{\partial y}\left(a,b\right)\right]$, where the production function

$f\left(x,y\right)=60x^{\frac{3}{4}}{y}^{\frac{1}{4}}$ is a function for revenue when $x$ units of labor and $y$ units of capital are

used. And $\frac{\partial f}{\partial x}\left(a,b\right)$ is wage per unit labor and $\frac{\partial f}{\partial x}\left(a,b\right)$ is wage per unit capital.