Factor 3x²−11x−20 . Rewrite the trinomial with the x-term expanded, using the two factors. Then, group the first two and last two terms together and find the GCF of each.

Answer 1

3x²-11x-20

First look at the first term, 3x² (3x )(x )

Next Look at last term, -20 Several way to get -20 by multiplying -1x20, -2x10, -4x5 place into last terms until when you FOIL OI term you get -11x Guess and Check, you will get good after some practice!

(3x - 1)(x+20) OI terms 20(3x)+ -1x = 59x NO!

(3x-2)(x+10) OI terms 10(3x) + -2x =28x NO!

(3x-4)(x+5) =5(3x) + -4x =11 x CLOSE we just need a -11x instead of 11 x so switch signs

(3x+4)(x-5) =-5(3x)+ 4x =-11x good :)

FOIL IT OUT 3x²-15x+4x-20 Now, group (3x²-15x)+(4x-20 )

Do a GCF for each group 3x(x-5) + 4(x-5)

Factor out (x-5)

(x-5)(3x+4)

Answer 2

(3x +4)(x-5) = 3x^2 -15x +4x -20 = x^2 -11x -20

3x^2 -15x = 3x(x-5)

4x-20 = 4(x-5)

add them

3x(x-5) + 4(x-5) factor out x-5

= (3x+4)(x-5)