polish doc of RMSPropOptimizer

python/paddle/fluid/optimizer.py

@@ -774,7 +774,7 @@ class RMSPropOptimizer(Optimizer):
 
     ..  math::
 
-        r(w, t) & = \\rho r(w, t-1) + (1 - \\rho)(\\nabla Q_{i}(w))^2 \\
+        r(w, t) & = \\rho r(w, t-1) + (1 - \\rho)(\\nabla Q_{i}(w))^2
 
         w & = w - \\frac{\\eta} {\\sqrt{r(w,t) + \\epsilon}} \\nabla Q_{i}(w)
 
@@ -786,7 +786,7 @@ class RMSPropOptimizer(Optimizer):
 
     ..  math::
 
-        r(w, t) & = \\rho r(w, t-1) + (1 - \\rho)(\\nabla Q_{i}(w))^2 \\\\
+        r(w, t) & = \\rho r(w, t-1) + (1 - \\rho)(\\nabla Q_{i}(w))^2
 
         v(w, t) & = \\beta v(w, t-1) + \\frac{\\eta} {\\sqrt{v(w,t) +
             \\epsilon}} \\nabla Q_{i}(w)