1. Notes 2.1 Order of Operations PEMDAS If an expression has only numbers and symbols, it is a numerical expression. If it has a variable it is a variable expression. Finding the value of an expression is called evaluating the expression. Steps to use when evaluating an expression: 1.Write the problem. 2.Substitute numbers for variables. 3.Solve

2. Example: a + 6 =, when a = 12 a + 6 = 12 + 6 = 18 Basic rules for evaluating expressions: 1.First do the operations within grouping symbols. 2.Then multiply and divide from left to right. 3.Finally add and subtract from left to right. Examples: 25 – 3 * 5 = (2 + 4) / 3 * 2 = 25 – 15 = 6 / 3 * 2 = 10 2 * 2 = 4

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4. homework answers 4) Sample: 4 x (3 + 2) / 1 Add: 3 + 2 4 x 5 / 1 Multiply: 4 x 5 20 / 1 Divide: 20/1 20 5) incorrect; addition was done before division 12 + 6 / 2 = 12 + 3 = 15

5. 6) incorrect; addition was done before the operation within the grouping symbols 3+4(7-5)=3+4(2)=3+8=11 7) 16 8) 10 9) 19 10) 8 11) 6 12) 4 13) 12 14) 8 15) 36 16) 2 17) 15 18) 64 19) t 20) f (6+10)/2=8 21) f (9+4)-(3+7)=3 22) t 23) f 15/(5-2)+14=19 24) f (8+16)/(2x2)=6 25) t 26) t 27) f (7+2)/(7-4)=3 28) 12x90/6=180 29) 14+6x3=32

6. 30) 15.7-14.25/5=12.85 31) 25.2-2.8x3=16.8 32) 5; 8; 11; 14; ans. Increase by 3. 33) 40; 28; 18; 10; ans. Decrease by 12, 10, and 8. 35) B 36) B 37) 5, 2, 1, 4, 3