How to Do Algebra Problems on the Calculator

Nongraphing calculators cannot solve algebra problems.

You can use a graphing calculator to solve algebra problems by locating the intersection of the equation's graphs. For equations with only one variable, the intersection of the two graphs tells you the value of x where both sides of the equation are equal, thereby making the equation true for that value of x. For two-variable equations, you will first have to isolate one of the variables in both equations before graphing. The intersection of the two graphed functions will tell you the values of x and y that solve the equation.

Things You'll Need

• TI-83 (or higher) graphing calculator

Instructions

Single Variable Equations

1. Go to the calculator's graphing menu by pressing the "Y=" button on the upper left (you may need to press "2nd" or the "Diamond" button first). Enter the left side of the equation on the Y1 line and press "Enter."

2. Enter the right side of the equation on the Y2 line of the graphing menu.

3. Press the "GRAPH" button to view the graphs of the two lines. You may need to adjust the graphing window to view both functions; choosing "ZFit" will ensure that both functions are visible onscreen.

4. Select "Intersection" from the "Math" menu (usually F5). You will be asked to choose the first and second curve; press "Enter" when they are highlighted. You may also be asked to choose a lower and upper bound: use the arrow keys to move to a point to the left of the intersection and press "Enter," and then move to a point to the right of the intersection and press "Enter" again.

5. You will see a readout with the x and y values of the intersection. The x value at the intersection is the solution to the equation.

Two Variable Equations

1. Isolate one of the two variables (usually y) for both equations by canceling terms. For example, in the equation 2y + 4 = 6x, you would cancel the "+4" by subtracting 4 from both sides to get 2y = 6x -4, then divide both sides by 2 to isolate the y: y = (6x - 4)/2 = 3x - 2.

2. Enter the two equations for y (or whichever variable you solved for) into the graphing menu at Y1 and Y2.

3. Find the intersection of the two lines using the same method as above. The y and x values at the intersection correspond to the solution for the variable you isolated and the other variable, respectively.

Tips & Warnings

• If the two lines do not intersect anywhere, they are parallel lines and there is no solution to the equation or system of equations.

References

• MathBits: Solving Equations
• Prentice Hall: How to Graph a Function on the TI-83/84