For example, to solve \(x^2 - 3x + 2 = 0\text{,}\)
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Enter EQN mode and select quadratic (option 3).
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Input coefficients: \(1\text{,}\) \(-3\text{,}\) \(2\text{.}\)
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Press = to solve. The calculator will show: \(X_1 = 1, \quad X_2 = 2\text{.}\)
Section 4.1 Zeros of Quadratic Functions Intro
Subsection 4.1.1 Solving Quadratic Equations with Scientific Calculator (EQN Mode)
My recommended calculator Casio FX-991ESPLUS2 (or some other similar scientific calculators) can find zeros of a quadratic function. You can use this to at least check your work, or help you out if you’re stuck.
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Press MODE, and go to equation mode by pressing EQN. A menu will appear which shows the various equation types. Press 3 to choose the quadratic equation option \(aX^2 + bX + c = 0\text{.}\)
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The calculator will show entry fields for \(a\text{,}\) \(b\text{,}\) and \(c\text{.}\) Your equation must be in this standard form \(ax^2+bx+c=0\text{.}\) Enter each coefficient in order.
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After entering all coefficients, press = (or EXE) to calculate the solutions.
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The calculator will display the first root as \(X_1 = \dots\text{.}\) Use the up/down arrow keys to scroll through the roots to see \(X_2 = \dots\text{.}\)
Example 4.1.1. Solving a Quadratic Equation.
Some notes:
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If there are repeated roots (so only one zero), the calculator will only display \(X = \dots\) with the single zero (as opposed to \(X_1 = \dots, X_2 = \dots\)).
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If there are no solutions, the calculator will output “complex numbers” that include the symbol \(i\text{.}\) This indicates there are no solutions.
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To go back to the regular calculator, press MODE and choose COMP mode (computation mode).
