$1x^4\left(-\frac{1}{x} \right )^0+4x^3\left(-\frac{1}{x} \right )^1+6x^2\left(-\frac{1}{x} \right )^2+4x^1\left(-\frac{1}{x} \right )^3+1x^0\left(-\frac{1}{x} \right )^4$