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Exercises Equations and inequalities

Example 9 from Algebra and Trigonometry, 2.5 Quadratic Equations

Solve the Quadratic Equation Using the Quadratic Formula

Solve the quadratic equation: $x^{2} + 5 x + 1 = 0.$

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Solution
Identify the coefficients: $a = 1, b = 5, c = 1.$ Then use the quadratic formula.

$\begin{matrix} x & = & \frac{- (5) \pm \sqrt{{(5)}^{2} - 4 (1) (1)}}{2 (1)} \\ = & \frac{- 5 \pm \sqrt{25 - 4}}{2} \\ = & \frac{- 5 \pm \sqrt{21}}{2} \end{matrix}$

How did it go?

PreviousSolving a Quadratic by Completing the Square Next Solving a Quadratic Equation with the Quadratic Formula

From Algebra and Trigonometry (1st edition) by OpenStax (Rice University), section 2.5, licensed under CC BY 4.0. Original at openstax.org. We split the solution into steps; the words, numbers and figures are the book's. OpenStax doesn't endorse this site.