How do i work this equation out?

3x^2 - 15x = 42

3x^2 - 15x - 42 = 0

using quadratic equation:

x = (15 +/- SQR(225 - 4(3)(-42)))/2(3)

x = (15 +/- 27)/6

x = -2, 7

- .--

3x^2 - 15x = 42 ==> x^2 - 5x = 14 (dividing throughout by 3)

==> x^2 - 5x - 14 = 0 == x^2 + 2x -7x -14 = 0 ==> x(x+2) - 7(x+2) ==> (x+2)(x-7) = 0

==> either x+2 = 0 or x-7 = 0 ==> x= -2 or x=7

3x^2 -15x = 42

3x^2 - 15x - 42 = 0

(x - 7) (3x+6) = 0

x - 7 = 0 3x + 6 = 0

3x = - 6

x = 7 x = - 2

First you move 42 to the other side then you get 3x^2 -15x-42 then you factor with 6and7 so it would be(3x+6)(x-7)

3x^2-21x+6x-42 foil

3x^2-15x=42

/3=

x^2-5x=14

x^2-5x-14=0

factorise- (x+2)(x-7)

x=-2 or x=7

hope you can see the process the get the answer.

3x^2 -15x -42 = 0

x^2 -5x -14 = 0

x^2 + 2x - 7x -14 = 0

x ( x+2) -7( x+ 2) = 0

( x-7) ( x+2) = 0

x = 7 OR -2 ANSWER

(3x + 6)(x - 7) = 0

x = -2 or +7

3x^2-15x-42=0

x=(15+sqrt((-15)^2-4(3)(-42)))/2(3)=7

x=(15-sqrt((-15)^2-4(3)(-42)))/2(3)=-2