Unit 2: Absolute Value Absolute Value Equations and Inequalities Absolute Value Inequalities Special Cases Absolute Value Models for Distance and Tolerance

– 3 3 Distance is greater than 3. Distance is 3. Distance is less than 3. By definition, the equation x = 3 can be solved by finding real numbers at a distance of three units from 0. Two numbers satisfy this equation, 3 and – 3. So the solution set is

Properties of Absolute Value For any positive number b:

SOLVING ABSOLUTE VALUE EQUATIONS Example 1 Solve a. Solution For the given expression 5 – 3x to have absolute value 12, it must represent either 12 or –12 . This requires applying Property 1, with a = 5 – 3x and b = 12.

Solve a. Solution or or or SOLVING ABSOLUTE VALUE EQUATIONS Example 1 Property 1 or Subtract 5. or Divide by – 3.

SOLVING ABSOLUTE VALUE EQUATIONS Example 1 Solve a. Solution or Divide by – 3. Check the solutions by substituting them in the original absolute value equation. The solution set is

Solve b. Solution or or or SOLVING ABSOLUTE VALUE EQUATIONS Example 1 Property 2 or or

Use Property 3, replacing a with 2x + 1 and b with 7. SOLVING ABSOLUTE VALUE INEQUALITIES Example 2 Solve a. Solution Use Property 3, replacing a with 2x + 1 and b with 7. Property 3 Subtract 1 from each part. Divide each part by 2.

The final inequality gives the solution set (– 4, 3). SOLVING ABSOLUTE VALUE INEQUALITIES Example 2 Solve a. Solution Divide each part by 2. The final inequality gives the solution set (– 4, 3).

Solve b. Solution or or or SOLVING ABSOLUTE VALUE INEQUALITIES Example 2 Solve b. Solution or Property 4 Subtract 1 from each side. or or Divide each part by 2.

Solve b. Solution or SOLVING ABSOLUTE VALUE INEQUALITIES Example 2 Divide each part by 2. or

Solve Solution or or or Example 3 Add 1 to each side. Property 4 SOLVING AN ABSOLUTE VALUE INEQUALITY REQUIRING A TRANSFORMATION Example 3 Solve Solution Add 1 to each side. or Property 4 or Subtract 2. Divide by – 7; reverse the direction of each inequality. or

Solve Solution or Example 3 SOLVING AN ABSOLUTE VALUE INEQUALITY REQUIRING A TRANSFORMATION Example 3 Solve Solution Divide by – 7; reverse the direction of each inequality. or

SOLVING SPECIAL CASES OF ABSOLUTE VALUE EQUATIONS AND INEQULAITIES Example 4 Solve a. Solution Since the absolute value of a number is always nonnegative, the inequality is always true. The solution set includes all real numbers.

SOLVING SPECIAL CASES OF ABSOLUTE VALUE EQUATIONS AND INEQULAITIES Example 4 Solve b. Solution There is no number whose absolute value is less than – 3 (or less than any negative number). The solution set is .

SOLVING SPECIAL CASES OF ABSOLUTE VALUE EQUATIONS AND INEQULAITIES Example 4 Solve c. Solution The absolute value of a number will be 0 only if that number is 0. Therefore, is equivalent to which has solution set {– 3}. Check by substituting into the original equation.

Write each statement using an absolute value inequality. USING ABSOLUTE INEQUALITIES TO DESCRIBE DISTANCES Example 5 Write each statement using an absolute value inequality. a. k is no less than 5 units from 8. Solution Since the distance from k to 8, written k – 8 or 8 – k , is no less than 5, the distance is greater than or equal to 5. This can be written as or equivalently

Write each statement using an absolute value inequality. USING ABSOLUTE INEQUALITIES TO DESCRIBE DISTANCES Example 5 Write each statement using an absolute value inequality. b. n is within .001 unit of 6. Solution This statement indicates that the distance between n and 6 is less than .001, written or equivalently

USING ABSOLUTE VALUE TO MODEL TOLERANCE Example 6 Suppose y = 2x + 1 and we want y to be within .01 unit of 4. For what values of x will this be true? Write an absolute value inequality. Solution Substitute 2x + 1 for y. Property 3 Add three to each part. Divide each part by 2.