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Solving Two-Step and 2-4 Multi-Step Inequalities Objective Solve inequalities that contain more than one operation. Holt McDougal Algebra 1 Solving Two-Step and 2-4 Multi-Step Inequalities Example 1A: Solving Multi-Step Inequalities Solve the inequality and graph the solutions. 45 + 2b > 61 45 + 2b > 61 –45 –45 Since 45 is added to 2b, subtract 45 from both sides to undo the addition. 2b > 16 b>8 0 2 4 6 Since b is multiplied by 2, divide both sides by 2 to undo the multiplication. 8 10 12 14 16 18 20 Holt McDougal Algebra 1 Solving Two-Step and 2-4 Multi-Step Inequalities Example 1B: Solving Multi-Step Inequalities Solve the inequality and graph the solutions. 8 – 3y ≥ 29 8 – 3y ≥ 29 –8 –8 Since 8 is added to –3y, subtract 8 from both sides to undo the addition. –3y ≥ 21 Since y is multiplied by –3, divide both sides by –3 to undo the multiplication. Change ≥ to ≤. y ≤ –7 –7 –10 –8 –6 –4 –2 Holt McDougal Algebra 1 0 2 4 6 8 10 Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 1a Solve the inequality and graph the solutions. –12 ≥ 3x + 6 –12 ≥ 3x + 6 –6 –6 Since 6 is added to 3x, subtract 6 from both sides to undo the addition. –18 ≥ 3x Since x is multiplied by 3, divide both sides by 3 to undo the multiplication. –6 ≥ x –10 –8 –6 –4 –2 Holt McDougal Algebra 1 0 2 4 6 8 10 Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 1b Solve the inequality and graph the solutions. Since x is divided by –2, multiply both sides by –2 to undo the division. Change > to <. x + 5 < –6 –5 –5 Since 5 is added to x, subtract 5 from both sides to undo the addition. x < –11 –11 –20 –16 –12 Holt McDougal Algebra 1 –8 –4 0 Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 1c Solve the inequality and graph the solutions. 1 – 2n ≥ 21 –1 –1 –2n ≥ 20 Since 1 – 2n is divided by 3, multiply both sides by 3 to undo the division. Since 1 is added to –2n, subtract 1 from both sides to undo the addition. Since n is multiplied by –2, divide both sides by –2 to undo the multiplication. Change ≥ to ≤. n ≤ –10 –10 –20 Holt McDougal Algebra 1 –16 –12 –8 –4 0 Solving Two-Step and 2-4 Multi-Step Inequalities Example 2A: Simplifying Before Solving Inequalities Solve the inequality and graph the solutions. 2 – (–10) > –4t 12 > –4t Combine like terms. Since t is multiplied by –4, divide both sides by –4 to undo the multiplication. Change > to <. –3 < t (or t > –3) –3 –10 –8 –6 –4 –2 Holt McDougal Algebra 1 0 2 4 6 8 10 Solving Two-Step and 2-4 Multi-Step Inequalities Example 2B: Simplifying Before Solving Inequalities Solve the inequality and graph the solutions. –4(2 – x) ≤ 8 –4(2 – x) ≤ 8 –4(2) – 4(–x) ≤ 8 –8 + 4x ≤ 8 +8 +8 4x ≤ 16 Distribute –4 on the left side. Since –8 is added to 4x, add 8 to both sides. Since x is multiplied by 4, divide both sides by 4 to undo the multiplication. x≤4 –10 –8 –6 –4 –2 Holt McDougal Algebra 1 0 2 4 6 8 10 Solving Two-Step and 2-4 Multi-Step Inequalities Example 2C: Simplifying Before Solving Inequalities Solve the inequality and graph the solutions. Multiply both sides by 6, the LCD of the fractions. Distribute 6 on the left side. 4f + 3 > 2 –3 –3 4f > –1 Holt McDougal Algebra 1 Since 3 is added to 4f, subtract 3 from both sides to undo the addition. Solving Two-Step and 2-4 Multi-Step Inequalities Example 2C Continued 4f > –1 Since f is multiplied by 4, divide both sides by 4 to undo the multiplication. 0 Holt McDougal Algebra 1 Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 2a Solve the inequality and graph the solutions. 2m + 5 > 52 2m + 5 > 25 –5>–5 2m > 20 m > 10 0 2 4 6 Simplify 52. Since 5 is added to 2m, subtract 5 from both sides to undo the addition. Since m is multiplied by 2, divide both sides by 2 to undo the multiplication. 8 10 12 14 16 18 20 Holt McDougal Algebra 1 Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 2b Solve the inequality and graph the solutions. 3 + 2(x + 4) > 3 Distribute 2 on the left side. 3 + 2(x + 4) > 3 3 + 2x + 8 > 3 Combine like terms. Since 11 is added to 2x, subtract 11 from both sides to undo the addition. 2x + 11 > 3 – 11 – 11 2x > –8 Since x is multiplied by 2, divide both sides by 2 to undo the multiplication. x > –4 –10 –8 –6 –4 –2 Holt McDougal Algebra 1 0 2 4 6 8 10 Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 2c Solve the inequality and graph the solutions. Multiply both sides by 8, the LCD of the fractions. Distribute 8 on the right side. 5 < 3x – 2 +2 +2 7 < 3x Holt McDougal Algebra 1 Since 2 is subtracted from 3x, add 2 to both sides to undo the subtraction. Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 2c Continued Solve the inequality and graph the solutions. 7 < 3x Since x is multiplied by 3, divide both sides by 3 to undo the multiplication. 0 2 4 Holt McDougal Algebra 1 6 8 10 Solving Two-Step and 2-4 Multi-Step Inequalities Example 3: Application To rent a certain vehicle, Rent-A-Ride charges $55.00 per day with unlimited miles. The cost of renting a similar vehicle at We Got Wheels is $38.00 per day plus $0.20 per mile. For what number of miles is the cost at Rent-A-Ride less than the cost at We Got Wheels? Let m represent the number of miles. The cost for Rent-A-Ride should be less than that of We Got Wheels. Cost at Rent-ARide must be less than 55 < Holt McDougal Algebra 1 daily cost at We Got Wheels 38 plus + $0.20 per mile 0.20 times # of miles. m Solving Two-Step and 2-4 Multi-Step Inequalities Example 3 Continued 55 < 38 + 0.20m Since 38 is added to 0.20m, subtract 55 < 38 + 0.20m 38 from both sides to undo the addition. –38 –38 17 < 0.20m Since m is multiplied by 0.20, divide both sides by 0.20 to undo the multiplication. 85 < m Rent-A-Ride costs less when the number of miles is more than 85. Holt McDougal Algebra 1 Solving Two-Step and 2-4 Multi-Step Inequalities Example 3 Continued Check Check the endpoint, 85. Check a number greater than 85. 55 = 38 + 0.20m 55 < 38 + 0.20m 55 38 + 0.20(85) 55 < 38 + 0.20(90) 55 55 38 + 17 55 55 < 38 + 18 55 < 56 Holt McDougal Algebra 1 Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 3 The average of Jim’s two test scores must be at least 90 to make an A in the class. Jim got a 95 on his first test. What grades can Jim get on his second test to make an A in the class? Let x represent the test score needed. The average score is the sum of each score divided by 2. First test score (95 plus second test score + Holt McDougal Algebra 1 x) divided by number of scores 2 is greater than or equal to ≥ total score 90 Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 3 Continued Since 95 + x is divided by 2, multiply both sides by 2 to undo the division. 95 + x ≥ 180 –95 –95 Since 95 is added to x, subtract 95 from both sides to undo the addition. x ≥ 85 The score on the second test must be 85 or higher. Holt McDougal Algebra 1 Solving Two-Step and 2-4 Multi-Step Inequalities Check It Out! Example 3 Continued Check Check the end point, 85. Check a number greater than 85. 90 90 90 90 Holt McDougal Algebra 1 90.5 ≥ 90