Argument error whenever I type equations with variables.

The syntax is probably wrong. See Screen capture below: You need to specify the unknown you are solving for.

Your function is not correctly defined. If graph is function y=f(x), variable must be x; if graph is polar, variable must be theta, and if graph is parametric, variable must be t. This does not cover all possible cases. Check the graph type and the definition of the function.

The calculator does have several error message concerning the argument. For the Request( command the syntax is
Request(Message, VarName)
What you type is stored as a string. It is only after you try to convert it to a value that the calculator looks at its content.
Here is an example where the variable VarName is x
Request ("Variable x", x)
I enter a complex number, manipulate it mildly with no apparent problem. However when I try to convert it to a numerical expression, and store it in the variable x, y, theta, I get a message Error non-real result.

variables not defined, 3/2 not a valid argument. How did this pop up under my bissell proheat 2 search?

You can see image below

Data type error meaning that an argument is of the wrong data type.
See captured image for the solution of your problem.

I believe you are using the wrong syntax for the commands.
diff ( function, variable) Example: diff (sin(x^2), x) sgould give you 2.x.cos(x^2)
expand( will expand an expression that has parentheses: expand( (a+b)^2) will give a^2+2a.b+b^2
Integrate $
$ ( tan^-1(x), x) willl give x.tan^-1(x) -(1/2) ln ('x^2+1')

Check the syntax of a command before using it. You will find the list of all comands and their syntax in the reference manual.

You already have something stored with the name x. Either get rid of it or use a different name for the variable of integration.

You can see what variables you have stored by pressing 2ND [VAR-LINK] (the minus key).

Hello,
My guess is that you entered as variable of the the functions, the name of a variable that is reserved (system variable, app variable ). In Home screen press [F6: Clean up][ Clear a-z] [ENTER] and stick with x as function argument.
Hope it helps.

Hello,
I am no seer, nor will I try to guess what may have happened. This error may come from various conditions
1. The most common reason is an omitted right parenthesis. For instance you press the [sin] function key. It shows as sin( , notice the right parenthesis. You enter the variable, say X, and you press [ENTER]. The calculator gives you a syntax error: It does not know what to do as long as you do not insert the closing parenthesis.
2. Another common source of this error message is the use of the regular MINUS sign instead of the (-). The latter appears on the scren as a smaller, raised minus sign. This is especially true when you want to raise a number or a variable to a negative exponent.

Every function has one way it takes in its food (argument). If you don't do it the right way, it gives you an error. The nice thing is that the calculator gives you the opportunity to correct the error. Whenever you see Error 1:quit 2: Go to, choose GO TO because the calculator shows you exactly the symbol that is creating havoc: It will be highlighted.

Hope it helps.