Question

-3|9x-7|=2 Find the answer for x

Answer 1

Solving Equations with Absolute Expressions

Answer:

No Solutions

Step-by-step explanation:

Given:

$-3|9x -7| = 2$

Rewriting the given equation:

$-3|9x -7| = 2 \\ |9x -7| = -\frac{2}{3}$

We have to realize that the right side of the equation, $|9x -7|$, will always be positive no matter what real values of $x$ (because we're taking the absolute value of the expression) and we are equating it to a negative constant number, $-\frac{2}{3}$. Something that is always positive will never be negative so there's no value for $x$ that satisfies the solution.

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Solving by positive of the expression:

$9x -7 = -\frac{2}{3} \\ 9x = -\frac{2}{3} +7 \\ 9x = -\frac{2}{3} +\frac{21}{3} \\ 9x = \frac{19}{3} \\ 9x \times \frac{1}{9} = \frac{19}{3} \times \frac{1}{9} \\ x = \frac{19}{27}$

Solving by the negative of the expression:

$-(9x -7)= -\frac{2}{3} \\ 9x -7 = \frac{2}{3} \\ 9x = \frac{2}{3} +7 \\ 9x = \frac{2}{3} +\frac{21}{3} \\ 9x = \frac{23}{3} \\ 9x \times \frac{1}{9} = \frac{23}{3} \times \frac{1}{9} \\ x = \frac{23}{27}$

Checking: $x = \frac{19}{27}$

$-3|9(\frac{19}{27}) -7| \stackrel{?}{=} 2 \\ -3|\frac{19}{3} -7| \stackrel{?}{=} 2 \\ -3|\frac{19}{3} -\frac{21}{3}| \stackrel{?}{=} 2 \\ -3|-\frac{2}{3}| \stackrel{?}{=} \\ -3(\frac{2}{3}) \stackrel{?}{=} 2 \\ -2 \stackrel{?}{=} 2 \\ -2 \neq 2$

$x = \frac{19}{27}$ is an extraneous solution.

Checking: $x = \frac{23}{27}$

$-3|9(\frac{23}{27}) -7| \stackrel{?}{=} 2 \\ -3|\frac{23}{3} -7| \stackrel{?}{=} 2 \\ -3|\frac{23}{3} -\frac{21}{3}| \stackrel{?}{=} 2 \\ -3|\frac{2}{3}| \stackrel{?}{=} \\ -3(\frac{2}{3}) \stackrel{?}{=} 2 \\ -2 \stackrel{?}{=} 2 \\ -2 \neq 2$

$x = \frac{23}{27}$ is an extraneous solution.