Help! I need an explanation of how to do this:

Question

(3x-1)(5x+4)

Answer 1

Sometimes referred to as the FOIL pattern:
F: multiply the First times the First ---> (3x)(5x) = 15x^2
O: multiply the Outers ----> (3x)(4) = 12x
I: multiply the Inners ----> (-1)(5x) = -5x
L: multiply the Lasts ----> (-1)(+4) = -4

add them up
15x^2 + 12x - 5x - 4
= 15x^2 + 7x - 4

Answer 2

Thanks @mathhelper ! it was correct

Answer 3

And it really helped! Hence your username