Help with A-math problem plzzz???

Question

Find the value of p and of q for which x^2 - 3x -4 is a factor of 2x^3 - px^2 - 5x + q

Answer 1

Hint:

Try to find p, q and r in the equation:

2x^3 - px^2 - 5x + q = (x^2 - 3x -4) * (2x + r)

(But first I recommend you to understand the meaning of this hint.)
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Answer 2

(x^2 - 3x - 4)(2x + a) = 2x^3 - (6 - a)x^2 - (8 + 3a)x - 4a
= 2x^3 - px^2 - 5x + q

(1) p = 6 - a
(2) 5 = 8 + 3a
(3) q = -4a

(2) => a = -1
(3) then is q = -4(-1) = 4
(1) then is p = 6 - (-1) = 7

p = 7 and q = 4