How do you factorise 10x-15?

Answer 1

It's quite simple really :)

What do 10 and 15 have in common? 5.

10 / 5 = 2

15 / 5 = 3

So you times 2 by 5 to get 10, and 3 by 5 to get 15!

Put 5 outside the brackets, and then put the two numbers inside the brackets. Since it's 10x, you know you will have to write 2x inside the brackets, and since it's -15, you have to write -3 (not +3!)

So the answer would be: 5(2x-3)

Check it by solving the equation - multiplying out of the brackets :)