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11-5

Solving Two-Step Inequalities. 11-5. Course 3. Warm Up. Problem of the Day. Lesson Presentation. Solving Two-Step Inequalities. 11-5. 7. 3. 11. 8. 16. 16. x = –. Course 3. Warm Up Solve. 1. 6 x + 36 = 2 x 2. 4 x – 13 = 15 + 5 x 3. 5( x – 3) = 2 x + 3 4. + x =.

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11-5

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  1. Solving Two-Step Inequalities 11-5 Course 3 Warm Up Problem of the Day Lesson Presentation

  2. Solving Two-Step Inequalities 11-5 7 3 11 8 16 16 x = – Course 3 Warm Up Solve. 1.6x + 36 = 2x 2. 4x – 13 = 15 + 5x 3. 5(x – 3) = 2x + 3 4. + x = x = –9 x = –28 x = 6

  3. Solving Two-Step Inequalities 11-5 Course 3 Problem of the Day Find an integer x that makes the following two inequalities true: 4 < x2 < 16 andx < 2.5 x = –3

  4. Solving Two-Step Inequalities 11-5 Course 3 Learn to solve two-step inequalities and graph the solutions of an inequality on a number line.

  5. Solving Two-Step Inequalities 11-5 Course 3 Solving a multistep inequality uses the same inverse operations as solving a multistep equation. Multiplying or dividing the inequality by a negative number reverses the inequality symbol.

  6. Solving Two-Step Inequalities 11-5 1 2 3 4 5 6 7 12 4x > 4 4 Course 3 Additional Example 1A: Solving Two-Step Inequalities Solve and graph. 4x + 1 > 13 4x + 1 > 13 – 1– 1Subtract 1 from both sides. 4x > 12 Divide both sides by 4. x > 3

  7. Solving Two-Step Inequalities 11-5 Remember! If both sides of an inequality are multiplied or divided by a negative number, the inequality symbol must be reversed. Course 3

  8. Solving Two-Step Inequalities 11-5  -6 -5 -4 -3 -2 -1 0 18 –9x –9 –9 Course 3 Additional Example 1B: Solving Two-Step Inequalities Solve and graph. –9x + 7  25 –9x + 7  25 – 7– 7Subtract 7 from both sides. –9x 18 Divide each side by –9; change  to . x–2

  9. Solving Two-Step Inequalities 11-5 1 2 3 4 5 6 7 10 5x > 5 5 Course 3 Check It Out: Example 1A Solve and graph. 5x + 2 > 12 5x + 2 > 12 – 2– 2Subtract 2 from both sides. 5x > 10 Divide both sides by 5. x > 2

  10. Solving Two-Step Inequalities 11-5  -6 -5 -4 -3 -2 -1 0 16 –4x –4 –4 Course 3 Check It Out: Example 1B –4x + 2  18 –4x + 2  18 – 2– 2Subtract 2 from both sides. –4x 16 Divide each side by –4; change  to . x–4

  11. Solving Two-Step Inequalities 11-5 +  20( + ) 20( ) 2x 2x 2x 2x 3 3 3 3 9 9 9 9 5 5 5 5 4 4 4 4 10 10 10 10 20( ) + 20( ) 20( ) Course 3 Additional Example 2: Solving Inequalities That Contain Fractions Solve +  and graph the solution. Multiply by LCD, 20. Distributive Property. 8x + 15 18 – 15– 15Subtract 15 from both sides. 8x 3

  12. Solving Two-Step Inequalities 11-5 Divide both sides by 8. x  8x 3 3 8 8 8 0 1 3 8 Course 3 Additional Example 2 Continued 8x 3

  13. Solving Two-Step Inequalities 11-5 +  Solve +  20( + )20( ) 3x 3x 3x 3x 1 1 1 1 5 5 5 5 5 5 5 5 4 4 4 4 10 10 10 10 20( ) + 20( ) 20 ( ) Course 3 Check It Out: Example 2 Multiply by LCD, 20. Distributive Property. 12x + 5 10 – 5– 5Subtract 5 from both sides. 12x 5

  14. Solving Two-Step Inequalities 11-5 x  Divide both sides by 12. 12x 5 5 12 12 12 0 5 12 Course 3 Check It Out: Example 2Continued 12x 5

  15. Solving Two-Step Inequalities 11-5 Course 3 Additional Example 3: School Application A school’s Spanish club is selling bumper stickers. They bought 100 bumper stickers for $55, and they have to give the company 15 cents for every sticker sold. If they plan to sell each bumper sticker for $1.25, how many do they have to sell to make a profit? Let R represent the revenue and C represent the cost. In order for the Spanish club to make a profit, the revenue must be greater than the cost. R > C

  16. Solving Two-Step Inequalities 11-5 Course 3 Additional Example 3 Continued The revenue from selling x bumper stickers at $1.25 each is 1.25x. The cost of selling x bumper stickers is the fixed cost plus the unit cost times the number of bumper stickers sold, or 55 + 0.15x. Substitute the expressions for R and C. Let x represent the number of bumper stickers sold. Fixed cost is $55. Unit cost is 15 cents. 1.25x > 55 + 0.15x

  17. Solving Two-Step Inequalities 11-5 55 > 1.10x 1.10 1.10 Course 3 Additional Example 3 Continued 1.25x > 55 + 0.15x Subtract 0.15x from both sides. – 0.15x– 0.15x 1.10x > 55 Divide both sides by 1.10. x > 50 The Spanish club must sell more than 50 bumper stickers to make a profit.

  18. Solving Two-Step Inequalities 11-5 Course 3 Check It Out: Example 3 A school’s French club is selling bumper stickers. They bought 200 bumper stickers for $45, and they have to give the company 25 cents for every sticker sold. If they plan to sell each bumper sticker for $2.50, how many do they have to sell to make a profit? Let R represent the revenue and C represent the cost. In order for the French club to make a profit, the revenue must be greater than the cost. R > C

  19. Solving Two-Step Inequalities 11-5 Course 3 Check It Out: Example 3 Continued The revenue from selling x bumper stickers at $2.50 each is 2.5x. The cost of selling x bumper stickers is the fixed cost plus the unit cost times the number of bumper stickers sold, or 45 + 0.25x. Substitute the expressions for R and C. Let x represent the number of bumper stickers sold. Fixed cost is $45. Unit cost is 25 cents. 2.5x > 45 + 0.25x

  20. Solving Two-Step Inequalities 11-5 45 > 2.25x 2.25 2.25 Course 3 Check It Out: Example 3 Continued 2.5x > 45 + 0.25x Subtract 0.25x from both sides. – 0.25x– 0.25x 2.25x > 45 Divide both sides by 2.25. x > 20 The French club must sell more than 20 bumper stickers to make a profit.

  21. Solving Two-Step Inequalities 11-5 2 3 3 8 1 4 -10 -9 -8 -7 -6 -5 -4 1 2 3 4 5 6 7 0 -18 -17 -16 -15 -14 -13 -12 1 2 w 3 8 Course 3 Insert Lesson Title Here Lesson Quiz: Part I Solve and graph. 1. 4x – 6 > 10 2. 7x + 9 < 3x – 15 3.w – 3w < 32 4.w +  x > 4 x < –6 w > –16

  22. Solving Two-Step Inequalities 11-5 Course 3 Lesson Quiz: Part II 5. Antonio has budgeted an average of $45 a month for entertainment. For the first five months of the year he has spent $48, $39, $60, $48, and $33. How much can Antonio spend in the sixth month without exceeding his average budget? no more than $42

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