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Multi-Step Inequalities

Solve inequalities with fractions and distribution

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Multi-Step Inequalities

What if you had an inequality with an unknown variable on both sides like 2(x2)>3x5? How could you isolate the variable to find its value? After completing this Concept, you'll be able to solve multi-step inequalities like this one.

Watch This

CK-12 Foundation: 0603S Solving Multi-Step Inequalities (H264)

Try This

For additional practice solving inequalities, try the online game at http://www.aaamath.com/equ725x7.htm#section2. If you’re having a hard time with multi-step inequalities, the video at http://www.schooltube.com/video/aa66df49e0af4f85a5e9/MultiStep-Inequalities will walk you through a few.

Guidance

In the last two sections, we considered very simple inequalities which required one step to obtain the solution. However, most inequalities require several steps to arrive at the solution. As with solving equations, we must use the order of operations to find the correct solution. In addition, remember that when we multiply or divide the inequality by a negative number, the direction of the inequality changes.

The general procedure for solving multi-step inequalities is almost exactly like the procedure for solving multi-step equations:

  1. Clear parentheses on both sides of the inequality and collect like terms.
  2. Add or subtract terms so the variable is on one side and the constant is on the other side of the inequality sign.
  3. Multiply and divide by whatever constants are attached to the variable. Remember to change the direction of the inequality if you multiply or divide by a negative number.

Example A

Solve the inequality 9x573x+12 and graph the solution set.

Solution

Original problem: 9x573x+12

Add 3x to both sides: 9x5+3x73x+3x+12

Simplify: 24x5712

Add 7 to both sides: 24x57+712+7

Simplify: 24x519

Multiply 5 to both sides: 524x5519

Simplify: 24x95

Divide both sides by 24: 24x249524

Simplify: x9524 Answer

Graph:

Example B

Solve the inequality 25x+1210x12 and graph the solution set.

Solution:

Original problem: 25x+1210x12

Add 10x to both sides: 25x+10x+1210x+10x12

Simplify: 15x+1212

Subtract 12: 15x+12121212

Simplify: 15x24

Divide both sides by -15: 15x152415 flip the inequality sign

Simplify: x85 Answer

Graph:

Example C

Solve the inequality 4x2(3x9)4(2x9).

Solution:

Original problem: 4x2(3x9)4(2x9)

Simplify parentheses: 4x6x+188x+36

Collect like terms: 2x+188x+36

Add 8x to both sides: 2x+8x+188x+8x+36

Simplify: 6x+1836

Subtract 18: 6x+18183618

Simplify: 6x18

Divide both sides by 6: 6x6186

Simplify: x3 Answer

Watch this video for help with the Examples above.

CK-12 Foundation: Solving Multi-Step Inequalities

Vocabulary

  • The answer to an inequality is usually an interval of values.
  • Solving inequalities works just like solving an equation. To solve, we isolate the variable on one side of the equation.
  • When multiplying or dividing both sides of an inequality by a negative number, you need to reverse the inequality.

Guided Practice

Solve the inequality 5x14>2(x+5).

Solution:

Original problem: 5x14>2(x+5)

Simplify parenthesis: 5x14>2x10

Multiply both sides by 4: 45x14>4(2x10)

Simplify: 5x1>8x40

Add 8x to both sides: 5x+8x1>8x+8x40

Simplify: 13x1>40

Add 1 to both sides: 13x1+1>40+1

Simplify: 13x>39

Divide both sides by 13: 13x13>3913

Simplify: x>3 Answer

Practice

Solve each multi-step inequality.

  1. 3x5<x+3
  2. x5>2x+3
  3. 2(x3)3x2
  4. 3(x+1)2x+5
  5. 2(x9)1(4x+7)
  6. x3<x+7
  7. \begin{align*}\frac{x}{4} < 2x-21\end{align*}
  8. \begin{align*}\frac{3(x-4)}{12} \le \frac{2x}{3}\end{align*}
  9. \begin{align*}2 \left ( \frac{x}{4} + 3\right ) > 6(x-1)\end{align*}
  10. \begin{align*}9x+4 \le -2 \left ( x+\frac{1}{2} \right )\end{align*}

Vocabulary

linear equation

linear equation

A linear equation is an equation between two variables that produces a straight line when graphed.

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