## Algebra 1 Tutorial

*Keeping Track of Minus Signs in Parentheses: Subtraction*

#### Intro

When evaluating an expression, the operations inside parentheses must be performed first.

So is the same as . Both are equal to 1. The correct treatment of plus and minus signs often causes confusion, especially when there are variables in the expression.

#### Sample Problem

You wish to solve the following equation for x.

To do so you must “get rid” of the parentheses.

#### Solution

On the left side of the equation we are subtracting a and a from . Remember that subtracting a negative is the same as adding a positive.

So the left side becomes ! In this case subtracting a negative 2x is the same as adding a positive 2x. Now we complete the problem.

……..6(x’s) plus (2 x’s) equals 8(x’s)

..adding 4 to both sides

……cancelling + and – 4 from the left

…………….side and summing the right side

……dividing both sides by 8

………………doing the division

CHECK

If

becomes

……substituting 3 for x

………doing the arithmetic

…..so we are right !

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