There are two kinds of equal signs in Real Answer™: “=” and “:=” .
When working in the Simultaneous Equation Set window, the two different kinds of equal signs do different things. Equations using “=” in that window tell Real Answer to find values of the variables which make the equations true. Statements using “:=” merely assign a value to a variable before the equation solving begins. Use “:=” to initialize variables to approximately what their solution values will be. Real Answer will then start with those estimates when you Run the “Solve Eq. Set” item in the solve menu (or use its command-key equivalent, “⌘R”). No matter where the “:=” assignment statements are placed in the Simultaneous Equation Set window, they will be executed before any of the “=” equations are solved. The advantage of having the “:=” equation sign available is that when it is used, you do not have to manually reset the value of the variables to their initial values every time you issue a “⌘R” command. If a variable is not initialized with a “:=”, it starts with whatever value it previously was given, either from prior, successfully completed Solve Simultaneous Equation Set commands, or assignments made in the Answers & Scratch window. If a variable has never been referred to before, it starts with an initial value close to 0.
In the Answers & Scratch window, you may assign a value to a variable with either an “=” or an “:=”. They mean the same thing-- assignment-- there. For consistency you could use “:=”, which means assignment no matter where it is used. However, it’s easier to type just “=” by pushing just the equal-sign key, so that is allowed as a short cut in the Answers & Scratch window.
