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(x + 1)(x – 3)(x – 4) = x3 – 6x2 + 5x + 12

I'm so sorry but I can't show any working for this as I don't have a clue how to factorise when there are no common letters and numbers? Thanks!

1 answer

It's already factored! You need to review how to multiply polynomials

It all hinges on the distributive property.

(x+1)(x-3) = x(x-3)+1(x-3)
= x^2-3x + x-3
= x^2-2x-3

Now multiply that by (x-4) and you have

(x^2-2x-3)(x-4)
= x^2(x-4)-2x(x-4)-3(x-4)
= x^3-4x^2-2x^2+8x-3x+12
= x^3-6x^2+5x+12