How to factorise? i need to factorise 4a^2 - 12b show method

4a² - 12b  =  4 (a² - 3b)
so you just pull out the common factor between the two term 4
then you divide each term by the common factor to find what remain
                                                            4a²/4 = a²
                                                           -12b/4= -3b
so now you put the four as the multiplier outside of the bracket and then put back the remainders:    4 ( a² - 3b)