Step by step
The question
Question: factor 6x + 15.
Factor means: write it as a times, with brackets.
6x + 15
1 Take out the common factor
A term is one part between the + and − signs.
A common factor goes into every term.
What goes into 6 and 15?
We list the numbers that go into each.
Into 6: 1, 2, 3, 6.
Into 15: 1, 3, 5, 15.
3 is the biggest one in both lists.
So the common factor is 3.
Into 6: 1, 2, 3, 6
Into 15: 1, 3, 5, 15
We divide every term by it.
What is left goes in the bracket.
6x ÷ 3 = 2x
15 ÷ 3 = 5
So it is 3(2x + 5).
= 3(2x + 5)
2 Check
Let's check: we multiply it back out.
The term in front times each part.
Check: 3(2x + 5) = 6x + 15
We get 6x + 15 again.
So 3(2x + 5) is right!
Let's look back.
First: take out the common factor.
Last: check.
Answer
= 3(2x + 5)