Solving quadratics by factoring review

Factoring quadratics makes it easier to find their solutions. This article reviews factoring techniques and gives you a chance to try some practice problems.

Example 1

Find the solutions of the equation.

2 x^{2} - 3 x - 20 = x^{2} + 34

\begin{aligned} 2 x^{2} - 3 x - 20 & = x^{2} + 34 \\ 2 x^{2} - 3 x - 20 - x^{2} - 34 & = 0 \\ x^{2} - 3 x - 54 & = 0 \\ (x + 6) (x - 9) & = 0 \end{aligned}

\begin{aligned} ↙ & ↘ \\ x + 6 & = 0 & x - 9 & = 0 \\ x & = - 6 & x & = 9 \end{aligned}

In conclusion, the solutions are $x = - 6$ ‍ and $x = 9$ ‍.

Want to see see another example? Check out this video.

Example 2

Find the solutions of the equation.

3 x^{2} + 33 x + 30 = 0

\begin{aligned} 3 x^{2} + 33 x + 30 & = 0 \\ x^{2} + 11 x + 10 & = 0 \\ (x + 1) (x + 10) & = 0 \end{aligned}

\begin{aligned} ↙ & ↘ \\ x + 1 & = 0 & x + 10 & = 0 \\ x & = - 1 & x & = - 10 \end{aligned}

In conclusion, the solutions are $x = - 1$ ‍ and $x = - 10$ ‍.

Want to see see another example? Check out this video.

Example 3

Find the solutions of the equation.

3 x^{2} - 9 x - 20 = x^{2} + 5 x + 16

\begin{aligned} 3 x^{2} - 9 x - 20 & = x^{2} + 5 x + 16 \\ 3 x^{2} - 9 x - 20 - x^{2} - 5 x - 16 & = 0 \\ 2 x^{2} - 14 x - 36 & = 0 \\ x^{2} - 7 x - 18 & = 0 \\ (x + 2) (x - 9) & = 0 \end{aligned}

\begin{aligned} ↙ & ↘ \\ x + 2 & = 0 & x - 9 & = 0 \\ x & = - 2 & x & = 9 \end{aligned}

In conclusion, the solutions are $x = - 2$ ‍ and $x = 9$ ‍.

Want to see see another example? Check out this video.

Practice

Problem 1

Solve for $x$ ‍.

x^{2} + 14 x + 49 = 0

x =

Want more practice? Check out these exercises:

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