Question

7. Using complete sentences, explain why it is necessary to have common denominators when adding or subtracting rational expressions.

Answer 1

"Using complete sentences"? Really?

No matter. It's easier to add 2/4 to 1/4 then it is to add 1/2 to 1/4.

Answer 2

if you are looking for a self-help guide, imagine you are asked to add $4 and £3.

you can't do it. because a dollar and a British pound are in different currencies or denominations. an apple that costs 4$ might cost 2£.

you either have to convert the £ to $ or the $ to £, so that you are adding apples to apples or pears to pears. or -- so that you using the same denominations(!!).

but you could also convert both £ and $ to say €.

so 1/3 + 1/4 -- you need the number on the bottom to be the same.

using the € example, convert the numbers (fractions) to a new denomination of 3*4 = 12.

you are now adding (1*4)/ 12 and (1*3)/12.