[solow] Update unfinished suggestions (#511)

* [solow] Update unfinished suggestions

* Update lectures/solow.md

* Revise context

---------

Co-authored-by: Matt McKay <mmcky@users.noreply.github.com>

Author: SylviaZhaooo

lectures/solow.md

@@ -55,9 +55,11 @@ $$
 Production functions with this property include
 
 * the **Cobb-Douglas** function $F(K, L) = A K^{\alpha}
-  L^{1-\alpha}$ with $0 \leq \alpha \leq 1$ and
+  L^{1-\alpha}$ with $0 \leq \alpha \leq 1$. 
 * the **CES** function $F(K, L) = \left\{ a K^\rho + b L^\rho \right\}^{1/\rho}$
-        with $a, b, \rho > 0$.
+        with $a, b, \rho > 0$. 
+        
+Here, $\alpha$ is the output elasticity of capital and $\rho$ is a parameter that determines the elasticity of substitution between capital and labor.
 
 We assume a closed economy, so aggregate domestic investment equals aggregate domestic
 saving.
@@ -81,6 +83,7 @@ Setting $k_t := K_t / L$ and using homogeneity of degree one now yields
 
 $$
     k_{t+1}
+    = s \frac{F(K_t, L)}{L} + (1 - \delta) \frac{K_t}{L}
     = s \frac{F(K_t, L)}{L} + (1 - \delta) k_t
     = s F(k_t, 1) + (1 - \delta) k_t
 $$