The electric potential at point (x, 0,0) is V=(1000/x+1500/x^2+500/x^3) volt. The electric field strength at a point x=1 m is \ \ \ \ i V / m.

The electric potential at point $\displaystyle (x, 0,0)$ is $\displaystyle V=\left(\frac{1000}{x}+\frac{1500}{x^2}+\frac{500}{x^3}\right)$ volt. The electric field strength at a point $\displaystyle x=1 \mathrm{~m}$ is \_\_\_\_ $\displaystyle \hat{i} \mathrm{~V} / \mathrm{m}$.