Update index.html

Author: jcponce

index.html

@@ -185,7 +185,7 @@ <h2 style="text-align: center;">WHAT IT IS ABOUT</h2>
             <p>What distinguishes this online book from other traditional texts in the first instance is the
                 use of interactive applets that allow you to explore properties of complex numbers
                 geometrically and analyze complex functions by using different techniques to visualize
-                them. For the design of applets I used the following open-source softwares:</p>
+                them. For the design of applets I used the following open-source software:</p>
 
             <div style=" text-wrap: wrap; display: flex; justify-content: center;">
                 <div style="padding: 0 5px;">
@@ -214,7 +214,7 @@ <h2 style="text-align: center;">WHAT IT IS ABOUT</h2>
                 to check existing ideas about our world, or as a tool to discover new phenomena
                 which then poses new ideas or challenges for their explanation.
                 Throughout the sections I have provided detailed instructions (in some cases)
-                to explore concepts and relationships about complex numbers using specific softwares,
+                to explore concepts and relationships about complex numbers using specific software,
                 nevertheless you must still keep in mind that computer hardware and software
                 are ephemeral things in comparison with mathematical ideas, which are timeless.</p>