How to solve a system of two equations
Enter two rows of coefficients to find x and y for a pair of linear equations.
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Use System of Equations mode when you need to solve two linear equations together. Before entering them, write each equation in the form:
This example solves:
The calculator reads each row as the coefficient of , the coefficient of , then the right-hand side. The two rows are therefore and . You do not enter the variables , , or the equals sign.
Enter both equations and solve the system
Below each step is the screen you should see after pressing.
Next to each step is the screen you should see after pressing.
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Step 1
Open the mode picker. On the 991CW-style keypad, choose HOME → Equation → Simultaneous → 2 unknowns; on other keypads, choose System of Equations → 2 unknowns. The first coefficient is selected in the two-equation grid.Press:
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Step 2
Enter , , and for the equation . Press the equals key after each number to confirm the cell and move to the next one.Press:
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Step 3
Enter , , and for the equation . Confirming the final cell with the equals key solves the system and shows , .Press:
Check the solution
Substitute and into the original equations:
Both equations are true, so the solution is:
The calculator treats an untouched coefficient cell as , so you do not need to enter zero for a missing term. For a negative coefficient, both the subtraction key and the negative-sign key are supported; this example uses the negative-sign key to enter .
Solve a system of two equations on your fx-991EX
Enter x + y = 5 and x − y = 1 and get x and y together — the keypad matches a real Casio calculator.