Update README.md (#1044)

README.md

@@ -25,10 +25,12 @@ result = optimize(rosenbrock, zeros(2), BFGS())
 ```
 This minimizes the [Rosenbrock function](https://en.wikipedia.org/wiki/Rosenbrock_function)
 
-<img src="https://user-images.githubusercontent.com/8431156/31627324-2bbc9ebc-b2ad-11e7-916f-857ad8dcb714.gif" title="f(x,y) = (a-x)^2+b(y-x^2)^2" />
+$$
+f(x, y) = (a - x)^2 + b(y - x^2)^2
+$$
 
-with a = 1, b = 100 and the initial values x=0, y=0.
-The minimum is at (a,a^2).
+with $a = 1$, $b = 100$ and the initial values $x=0$, $y=0$.
+The minimum is at $(a,a^2)$.
 
 The above code gives the output
 ```jlcon