If $$v = (x^2 + y^2 + z^2)^{\frac {-1}{2}}$$, then $$\frac{\partial^2 v}{\partial x^2} + \frac{\partial^2 v}{\partial y^2} + \frac{\partial^2 v}{\partial z^2}$$ is
Create a FREE account and get:
CAT Averages, Ratios & Proportions
CAT Logarithms, Surds & Indices