Subtract Expressions

Add and Subtract Rational Expressions

by Ashley Dugas

Multiple Choice

What would be the common denominator for this expression?

• $$3a$$  

• $$2$$  

• $$6a$$  

• $$5a$$  

​When in doubt...

​Multiply the denominators to create a common denominator

Multiple Select

What would be the common denominator for this expression?

• $$6b^2$$  

• $$2b$$  

• $$6b$$  

• $$2b^2$$  

​Which is best?

​When in doubt, take the product of the two denominators. You can always simplify later.

​

​Work smart! Stop and see if the expressions can be simplified before working.

Multiple Choice

What would be the common denominator for this expression?

• $$2x^2$$  

• $$2x$$  

• $$2x+1$$  

• Doesn't exist

​Rewrite Fractions

​Any constant or term can be written with a denominator of 1.

​

​Then to find the common denominator, multiply the original denominators.

Multiple Choice

What would be the common denominator for this rational expression?

• $$z$$  

• $$z\left(z+2\right)$$  

• $$z^2+2$$  

• $$z^2$$  

​When in doubt...

​Multiply the denominators to create a common denominator

​HINT! Leave denominator in factored form! It makes it easier to simplify if need be.