Inverse operations and Writing expressions Objective: 1. Learn to use inverse operations. 2. Write verbal phrases and sentences as simple as algebraic expressions.

4.1 Inverse operations Suppose that you ride your bike north for 4 miles, and then decide you need to return home, where you started. What would you have to do? _____________________________.Suppose that you ride your bike north for 4 miles, and then decide you need to return home, where you started. What would you have to do? _____________________________. Riding north and riding south are inverse actions because theyeach other.Riding north and riding south are inverse actions because they undo each other.

If you add 5 to a number and you want to return to the original number, you started with, you would subtract 5. Addition and subtraction are inverse operations because they “undo”each other. Undo each action. Find the inverse operation. 1.Add 3: ____________ 2.Go up the stairs: _________________________ 3.Drive 5 miles east: ______________________ 4. Turn off the lights: ______________________ 5. Talk in class: ___________________________ 6. Divide by 65: ___________________________

4.2 Writing Expressions An algebraic expression is an expression that contains a variable. For example: x – 4 or 5(n+3) When solving a problem you may have to translate words of phrases into algebraic expressions. The following chart shows the operations that may be suggested by words or phrases: AdditionSubtractionMultiplication Division plus minusTimesDivided by sumdifferenceproductquotient More thanLess thanDouble, triple…Half of Increased byDecreased bybySeparate equally… Gain ofLessofper

Examples Write a phrase for each algebraic expression X (5-R) 3. 2K +6 Write an algebraic expression for each phrase Five less than a number C 2. 2.Four times the sum of a number N and Six more than a number X Write an algebraic expression for each phrase Five less than a number C 2. 2.Four times the sum of a number N and Six more than a number X

homework Write a phrase for each algebraic expression m 2. 6 – W 3. 2(b-5) 4. N a + 2b Write an algebraic expression for each phrase Fifteen increased by T 2. 2.A number M decreased by ten 3. 3.The product of R and eight 4. 4.Five years older than Luis 5. 5.Twice as many oranges. Write an algebraic expression for each phrase Fifteen increased by T 2. 2.A number M decreased by ten 3. 3.The product of R and eight 4. 4.Five years older than Luis 5. 5.Twice as many oranges.