你需要解决（6.3）$G_R$，这里是一步一步：

$G_w = \frac{G_R(z) G_P(z)}{1 + G_R(z) G_P(z)}$, 两边乘以$1 + G_R(z) G_P(z)$要得到：

$G_R(z)G_w(z)G_P(z) - G_R(z)G_P(z) = -G_w$, 现在求解$G_R(z)$：

$G_R(z) = -\frac{G_w(z)}{G_w(z)G_P(z) - G_P(z)} = -\frac{G_w(z)}{G_P(z)(G_w(z) -1)} = \frac{1}{G_P(z)}\frac{G_w(z)}{1 - G_w(z)}$

你解方程（6.3）为$G_R$.