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Sign Rules for Addition If the terms have the same sign (both positive or both negative): Add them & keep the sign If the terms have different signs (one positive and one negative): Subtract them (big minus small) & keep the sign of the big number

Combine -4 and -5 Same Signs: Add & keep the sign 2. keep the negative = Add the numbers: = 9 Combine 6 and 8 2. keep the positive = Add the numbers: = 14 Note: Numbers that have no sign in front (on their left) are “understood” to be positive

Combine -3 and 7 Different Signs: Subtract & keep the sign of the bigger number 2. keep the sign of the bigger number ( +7 is bigger than -3) = 4 Combine -10 and 7 = Subtract the numbers: = 4 (Big - small: 7 is bigger than 3) 1. Subtract the numbers: = 3 (Big - small: 10 is bigger than 7) 2. keep the sign of the bigger number ( -10 is bigger than +7)

Sign Rules for Multiplication Count the number of negative (minus) signs in the problem If it has an odd number of negatives: The answer will be negative If it has an even number of negatives: The answer will be positive

Odd number of negatives: Odd number of negatives: Answers are negative 2. Answer is negative = -40 Combine -3(-4)(-7) -14(-1) 2. Answer is negative = Count negatives: -4(-5)(2)(-1) (3 negatives): 3 is an ODD number 1. Count negatives: -3(-4)(-7) -14(-1) (5 negatives): 5 is an ODD number Combine -4(-5)(2)(-1)

Even number of negatives: Even number of negatives: Answers are positive 2. Answer is positive = 60 Combine -5(2)(-6) -4(-1) 2. Answer is positive = Count negatives: 4(-5)(-3) (2 negatives): 2 is an EVEN number 1. Count negatives: -5(2)(-6) -4(-1) (4 negatives): 4 is an EVEN number Combine 4(-5)(-3)

Practice Problems: (Hit enter to see the answers) 1) (-6)(7) 5) 5(-1)(-2) 2) 5(-9)(-2) 6) -(-2)(8) 3) -(-3)(-10) 7) (4)(-1)(1)(-1)(-8) 4) -(-8)(-6)(-2) 8) (-11)(-12) Answers: 1) -42 2) 90 3) -30 4) -48 5) 5/6 6) 16 7) -32 8) 132 (-2) (-3)(4) -

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