How to solve for any variable?

• You have several memory locations you can use to store values in them. The memory locations are A,B,C,D, M, X, and Y. You use [SHIFT][RCL] and one of the variable names above. Example store 78 in C location: 78 [SHIFT] [RCL] [HYP]. To recall that value press [RCL] [HYP]

• If you want to use the EQN (equation solving mode, press [MODE][5:EQN] then select the equation type . For example [3:aX^2+bX+c=0] will display a template wher you input the three coefficients.

• You can also enter any type of equation and solve it with the SOLVE command. In that case you use the keyboard to enter the expression (see above how to enter variable name X). To type in the equal sign (=) use [ALPHA][ CALC]. Once the whole equation is typed in, press [SHIFT[ [SOLVE], and the calculator will prompt SOLVE for X? Confirm and press the main = sign. Press = again to get a second, a third root (if any)

Ok, I will tell you how to enter expressions in your calculator, but you will not be able to 'solve' the equation you gave as example because you can only find y in terms of x or find x in terms of y. To solve for x and for y you need a second linear equation. You must have a system of two simultaneous linear equations.

You can enter equations of any type. Read the rest of the post. Keep in mind that if you are using the Solve( function X must be the unknown. If you are using the Table computational mode, X is the independent variable and Y the dependent one.

The variables you have at your disposal in this calculator are
A, B,C,D,X,Y,M. All of them are accessed by pressing the [ALPHA] key before the key near which is written the name of the variable. You will notice that the markings of the symbols accessed with the [ALPHA] key are of the same color as that of the [ALPHA] key.

You will notice also that there are two = signs.
The one at the bottom right executes the command line. By pressing it you find the result of the expression just entered.

The other = sign is marked on the body of the calculator with the same color as the [ALPHA] key. It is located at the top left of the keyboard (excluding the row with SHIFT, MODE, the navigation buttons)

Example to enter X^2-2X-35=0 you proceed as follows.
Direct access physical keys are in [ ],
[ALPHA] (X) [X to power 2] [ - ] [2] [ * ][ALPHA] (X) [ - ] [3][5] [ALPHA] (=) [0]

Usually when you enter such an expression it is with the intention of solving it for X. By default X is taken to be the UNKNOWN. You will be prompted to enter the value assigned to any other letter symbol (Y, A,B,C,D).

So, if you want to use the Solve function, you enter the equation you are dealing with, and before pressing anything else, press [SHIFT] [CALC] and the calculator will ask you a question: "Solve for X?" , and you press the = sign at the bottom right.
Then you will be prompted for any other non-X letter. Once all non-X variables (if any) are given values, the calculator will return with the solution. You will see on the screen L-R= (should be zero if you are lucky).

You can enter equations of any type. Read the rest of the post. Keep in mind that if you are using the Solve( function X must be the unknown. If you are using the Table computational mode, X is the independent variable and Y the dependent one.

The variables you have at your disposal in this calculator are
A, B,C,D,X,Y,M. All of them are accessed by pressing the [ALPHA] key before the key near which is written the name of the variable. You will notice that the markings of the symbols accessed with the [ALPHA] key are of the same color as that of the [ALPHA] key.

You will notice also that there are two = signs.
The one at the bottom right executes the command line. By pressing it you find the result of the expression just entered.

The other = sign is marked on the body of the calculator with the same color as the [ALPHA] key. It is located at the top left of the keyboard (excluding the row with SHIFT, MODE, the navigation buttons)

Example to enter X^2-2X-35=0 you proceed as follows.
Direct access physical keys are in [ ],
[ALPHA] (X) [X to power 2] [ - ] [2] [ * ][ALPHA][(X) [ - ] [3][5] [ALPHA] (=) [0]

Usually when you enter such an expression it is with the intention of solving it for X. By default X is taken to be the UNKNOWN. You will be prompted to enter the value assigned to any other letter symbol (Y, A,B,C,D).

So, if you want to use the Solve function, you enter the equation you are dealing with, and before pressing anything else, press [SHIFT] [CALC] and the calculator will ask you a question: "Solve for X?" , and you press the = sign at the bottom right.
Then you will be prompted for any other non-X letter. Once all non-X variables (if any) are given values, the calculator will return with the solution. You will see on the screen L-R= (should be zero if you are lucky).

You cannot solve this equation,at least not in the regular meaning of solving which is to find the roots. This is a relation linking two variables x and y, in other words a function. There are an infinite number of orderd pairs tha satisfy this equation.
You can draw it as y=1/5(-4x 12) but your calculator cannot graph.
If you want to use the Solve( command on this calculator you must supply the value of y.

Rename your variable (unknown) X, because the calculator takes X as the default unknown. It will ask you "Solve for X?"
the 7, the second minus sign, 3 and 11 use the relevant keys.
For the first minus sign use the negation key or change sign (-)
For the variable X, examine the calculator keys on the row where the parentheses are. To the right corner of the key area there is a symbol in the same color as the ALPHA key. I believe the X is under the right parenthesis, or thereby.
To enter the X variable you press [ALPHA][ )]. To enter the = sign, you press [ALPHA] [CALC].

To execute the solve command, press [SHIFT] [CALC] and you will be prompted " Solve for X?"

Hello,

Sorry, but what you wrote is not an equation but a polynomial expression. You want to solve the equation x^4+5x^3-3x^2-43x-60 =0.

The solve( command, can only be used with real numbers.
The solve( is available through the CATALOG : [2nd][CATALOG], scroll down till you reach the command. Highlight it and press [ENTER]. The command echodes on main screen as solve( .
You complete the command by entering the expression (not the equation), the name of the variable you solve for, the initial guess , and { lower limit, upper limit} between curly brackets, and the closing parenthesis.
Exemple:
solve (x^4+5x^3-3x^2-43x-60 , x,0 {-5,0} ) [ENTER]
should give you the negative root,
solve (x^4+5x^3-3x^2-43x-60 , x,0 {0,5} ) [ENTER]
should give you the positive root.

It is implied that the expression is 0, so you should not insert =0, otherwise you get an error. Here for the lower limit is -5 you must use the change sign symbol (-) under the 3 key, not the regular MINUS.

You may ask how I knew that there were two roots when the equation is a quartic? By first graphing it to have an idea about where the roots lie and how many there are. You should always do that to speed up the search.

There is another way to zoom in on the roots: by drawing the graph and using the tools accessible under the [2nd][CALC] menu, namely the option [2:Zero]
The resolution of the TI83/84 is not good enough for this function that grows too fast, but I am inserting a picture of the curve from another calculator with a much better resolution.



Hope it helps.

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Type it like this: solve( equation1 and equation2 and moreEquations, {list of variables to solve for})

Put all of your equations right after the opening parenthesis separated by the word and, then a comma, then within curly braces each variable you want to solve for each separated by a comma.

The TI-30XA cannot solve algebraic equations. You need a more advanced calculator for that, like the TI-89.

Regards,
javabytes

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