Question

factor 3x^2-14x-40
I got x=4, x= -10/3
is that correct?

Answer 1

recheck ur answer

Answer 2

3x^2 - 20x + 6x - 40

Answer 3

3x-40 = -120

you want two numbers to multiply to give -120 and add to make -14

-20+6 does this for us

so you replace -14x with -20x + 6x your new equation is

3x²+6x-20x-40

now you can factorise this by taking a factor of 3x out of 3x²+6x

this gives

3x(x+2)

then you can take a factor of -20 out of -20x-40

this gives

-20(x+2)

your factorised form is

(3x-20)(x+2)


you can work x out from this

Answer 4

@ebby07 are u here?

Answer 5

Thank you, so whenever you can not factor out the problem you times 3x(-40)?

Answer 6

I am having trouble with the factoring so I just want to make sure I understand it

Answer 7

so now u understand it bcoz @amorfide explain it quite brillant

Answer 8

when ever the coefficient of x² is greater than 1 you will multiply the constant by the coefficient of x² then you will try to find two numbers to multiply to give that number but they must also add together to give the coefficient of x so you had 3x^2-14x-40 you do 3 times -40 this gives you -120 you will write out numbers which multiply to give -120 1 x -120 2 x -60 3 x -40 4 x -30 5 x -24 6 x -20 <<< this adds to give -14 which is your coefficient of x and mutliplies to give you your new constants -120 this replaces 14x so instead of 14 x you have 6x-20x which is equal to 14 x you do this to make it easy to factorise so now you rewrite the equation 3x²+6x-20x-40

Answer 9

lol this messed up oops might be hard to read...

Answer 10

Thank you for the explanation