7.4 Subtracting Algebraic Expressions

7.4 Subtracting Algebraic Expressions

Multiple Choice

WARM UP

Add these expressions:

 $\left(x-5\right)+\left(2x+3\right)$  

• x + 2
  

• 3x + 8

• 3x - 2

• 3x + 2

Subtracting Expressions

• Subtracting Expressions is very similar to adding expressions

• The only difference is that we need to distribute the minus sign (negative) to the second expression

• Example:

   $\left(2x+1\right)-\left(x+5\right)$ 

•       $2x+1-x-5$  

•          $x-4$      DONE! 

Practice:

•  $\left(3x+4\right)-\left(2x-1\right)$  

•        $3x+4-2x+1$  

•          $x+5$    DONE!

Open Ended

Try it:

 $\left(10x-1\right)-\left(3x+2\right)$  

 $\left(10x-1\right)-\left(3x+2\right)$  

• Distribute the negative

•                                                 $10x-1-3x-2$  

• Combine Like-Terms

•                                                      $7x-3$   Done! 

Practice:

•  $\left(-2x-1\right)-\left(-10x+4\right)$  

•         $-2x-1+10x-4$  

•                     $8x-5$      DONE!

Open Ended

Try it:

 $\left(12x+2\right)-\left(-3x-1\right)$  

 $\left(12x+2\right)-\left(-3x-1\right)$  

•         $12x+2+3x+1$  

•                $15x+3$     DONE!

Larger Expressions

•       $\left(5xy+2y\right)-\left(3xy+7x-4y\right)$  

•          $5xy+2y-3xy-7x+4y$  

•                    $2xy+6y-7x$    DONE!

Open Ended

Try It:

 $\left(2x+3xy-8y\right)-\left(x+10y-2xy\right)$  

Practice:

• Two friends went to the store to buy some fruit. Jackson bought a watermelon that costs $5 and 3 bags of cherries. Liam bought a pineapple that costs $3 and 2 bags of cherries.

• Write an expression for the total amount of money each friend spent, then find the difference between the expressions.

Multiple Choice

What is the expression for Jackson's total amount, who bought a watermelon for $5 and 3 bags of cherries?

• 3x + 5

• 5x + 3

• 3x - 5

• 8x

Multiple Choice

What is the expression for Liam's total amount, who bought a pineapple for $3 and 2 bags of cherries?

• 3x - 2

• 2x

• x + 3

• 2x + 3

Open Ended

Find the Difference

 $\left(3x+5\right)-\left(2x+3\right)$  

Reflection

• If a bag of cherries cost $1, how much more did Jackson spend than Liam?

• The difference was  $x+2$ , where x = cost of cherries

Multiple Choice

Exit Ticket 3/9:

 $\left(15xy+2y\right)-\left(-2x+3y\right)$ 

•  $13xy+5y$  

•  $17xy+2y+2x$  

•  $15xy+5y+2x$