Question

Factor.

3a-15

Answer 1

3(a-5)

Answer 2

also \[6x ^{2}+9x\]

Answer 3

Do you understand how your first factor question was solved?
You need to see what is common in both terms, so in the second question you have x in both terms so you can take that out:
x(6x+9)
then you notice that 6 is divisible by three and so is 9 (ie 6/3 = 2 and 9/3 = 3) so taking that out the brackets you get
3x(2x+3)
you can check your answer by multiplying everything inside the brackets by what is outside, if you get the same thing you started from, you've got the right answer, if not, something is wrong.