Pre-Algebra : Absolute Value

Study concepts, example questions & explanations for Pre-Algebra

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Example Questions

Example Question #321 : Operations And Properties

Solve for \displaystyle x

\displaystyle \left | x+1\right |=3

Possible Answers:

\displaystyle 2, 3

\displaystyle 3

\displaystyle -4

\displaystyle 2

\displaystyle -4, 2

Correct answer:

\displaystyle -4, 2

Explanation:

When taking absolute values, we need to consider both positive and negative values. So, we have two equations. \displaystyle -(x+1)=3, x+1=3 

For the left equation, we can switch the minus sign to the other side to get \displaystyle x+1=-3. When we subtract \displaystyle 1 on both sides, we get \displaystyle x=-4.

For the right equation, just subtract \displaystyle 1 on both sides, we get \displaystyle x=2.

\displaystyle x=2, x=-4

Example Question #322 : Operations And Properties

Solve for \displaystyle x.

\displaystyle \left | 4x\right |=12

Possible Answers:

\displaystyle \pm3

\displaystyle 12

\displaystyle 3

\displaystyle -3

\displaystyle 0

Correct answer:

\displaystyle \pm3

Explanation:

When taking absolute values, we need to consider both positive and negative values. So, we have two equations. \displaystyle 4x=12, -(4x)=12 

For the left equation, when we divide both sides by \displaystyle 4\displaystyle x=3

For the right equation, we distribute the negative sign to get \displaystyle -4x=12. When we divide both sides by \displaystyle -4\displaystyle x=-3

\displaystyle x=3, x=-3

Example Question #323 : Operations And Properties

Solve for \displaystyle x.

\displaystyle \left | 2x\right |+5=9

 

Possible Answers:

\displaystyle 2

\displaystyle \pm2

\displaystyle -2

\displaystyle -4

\displaystyle -2, -4

Correct answer:

\displaystyle \pm2

Explanation:

When taking absolute values, we need to consider both positive and negative values. Let's first subtract \displaystyle 5 on both sides. So, we have two equations. \displaystyle 2x=4, -(2x)=4 

For the left equation, when we divide both sides by \displaystyle 2\displaystyle x=2

For the right equation, we distribute the negative sign to get \displaystyle -2x=4. When we divide both sides by \displaystyle -2\displaystyle x=-2

\displaystyle x=2, x=-2

Example Question #324 : Operations And Properties

Solve for \displaystyle x.

\displaystyle 16+4x=4+2\left | x\right |

Possible Answers:

\displaystyle -2

\displaystyle 2,6

\displaystyle -6

\displaystyle 2

\displaystyle -2, -6

Correct answer:

\displaystyle -2

Explanation:

When taking absolute values, we need to consider both positive and negative values. So, we have two equations. \displaystyle 16+4x=4+2x, 16+4x=4-2x 

For the left equation, we subtract \displaystyle 4 on both sides and subtract \displaystyle 4x on both sides. We now have \displaystyle 12=-2x. When we divide both sides by \displaystyle -2\displaystyle x=-6

For the right equation, we subtract \displaystyle 4 on both sides and subtract \displaystyle 4x on both sides. We now have \displaystyle 12=-6x. When we divide both sides by \displaystyle -6\displaystyle x=-2

Let's double check. When we plug in \displaystyle -6, both sides aren't equal.

\displaystyle 16+4(-6)=4+2\left | -6\right |

\displaystyle 16-24=4+12

\displaystyle -8\neq16

But if we plug in \displaystyle -2, we get both sides equal.

\displaystyle 16+4(-2)=4+2\left | -2\right |

\displaystyle 16-8=4+4

\displaystyle 8=8

So \displaystyle -2 is the only answer. 

Example Question #331 : Operations And Properties

Solve for \displaystyle x.

\displaystyle 3-\left | x\right |=5

Possible Answers:

No possible answer

\displaystyle \pm2

\displaystyle -2

\displaystyle 8

\displaystyle 2

Correct answer:

No possible answer

Explanation:

Let's isolate the variable by subtracting both sides by \displaystyle 3. We have:

\displaystyle -\left | x\right |=2 This will be a contradicting expression. Absolute values always generate positive values and since there's a negatie sign in front of it, it will never match a positive value. Therefore no possible answer exist. 

Example Question #332 : Operations And Properties

Solve for \displaystyle x.

\displaystyle \left | x\right |-6=0

Possible Answers:

\displaystyle 3

\displaystyle -6

\displaystyle 6

\displaystyle \pm6

\displaystyle 0

Correct answer:

\displaystyle \pm6

Explanation:

When taking absolute values, we need to consider both positive and negative values. So, we have two equations. \displaystyle -x-6=0, x-6=0 

For the left side, we add \displaystyle 6 to both sides and shift the negative sign to the other side to get \displaystyle x=-6.

For the right side, we add \displaystyle 6 to both sides and \displaystyle x=6.

\displaystyle x=6, x=-6

Example Question #332 : Operations And Properties

Solve for \displaystyle x.

\displaystyle 6+\left | x\right |=0

Possible Answers:

\displaystyle 0

\displaystyle -6

No possible answer

\displaystyle 6

\displaystyle \pm6

Correct answer:

No possible answer

Explanation:

Let's isolate the variable by subtracting both sides by \displaystyle 6. We have:

\displaystyle \left | x\right |=-6 This will be a contradicting expression. Absolute values always generate positive values. Therefore no possible answer exist. 

Example Question #334 : Operations And Properties

Solve for \displaystyle x.

\displaystyle \frac{6}{\left | x\right |}=9

Possible Answers:

\displaystyle 9

\displaystyle \frac{3}{2}

\displaystyle \pm \frac{3}{2}

\displaystyle \pm \frac{2}{3}

\displaystyle \frac{2}{3}

Correct answer:

\displaystyle \pm \frac{2}{3}

Explanation:

When taking absolute values, we need to consider both positive and negative values. Let's multiply both sides by \displaystyle \left | x\right | to get rid of the fraction. So, we have two equations. \displaystyle 9x=6, -(9x)=6 

For the left equation, when we divide both sides by \displaystyle 9\displaystyle x=\frac{2}{3}

For the right equation, we distribute the negative sign to get \displaystyle -9x=6. When we divide both sides by \displaystyle -9\displaystyle x=-\frac{2}{3}

\displaystyle x=\frac{2}{3}, x=-\frac{2}{3}

Example Question #335 : Operations And Properties

Solve for \displaystyle x

\displaystyle \frac{\left | 4x\right |}{3}=8

Possible Answers:

\displaystyle \pm6

\displaystyle \frac{1}{6}

\displaystyle \pm \frac{1}{6}

\displaystyle 12

\displaystyle 6

Correct answer:

\displaystyle \pm6

Explanation:

When taking absolute values, we need to consider both positive and negative values. Let's multiply each side by \displaystyle 3 to get rid of the fraction. So, we have two equations. \displaystyle 4x=24, -(4x)=24 

For the left equation, when we divide both sides by \displaystyle 4\displaystyle x=6

For the right equation, we distribute the negative sign to get \displaystyle -4x=24. When we divide both sides by \displaystyle -4\displaystyle x=-6

\displaystyle x=6, x=-6

Example Question #333 : Operations And Properties

Solve for \displaystyle x.

\displaystyle \left | x\right |=17

Possible Answers:

\displaystyle 0

\displaystyle 0, 17

\displaystyle 17

\displaystyle \pm17

\displaystyle -17

Correct answer:

\displaystyle \pm17

Explanation:

When taking absolute values, we need to consider both positive and negative values. So, we have two answers. \displaystyle x=17, x=-17

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