If x=-5 is a zero, then the first factor of the polynomial would be (x + 5 )
To find the other two factors we can divide the polynomial by the expression (x+5).
Using synthetic division, we have:
-5 I 4 15 -24 5 (Coefficients of the dividend)
I -20 25 -5 (Multiplying each coefficient by the results of the substraction and adding)
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4 -5 1 0 (Coefficients of the quotient)
The result of the division is 4x^2 - 5x + 1. Factoring it, we have:
4x^2 - 4x -x + 1 (Separating -5x into -x and -4x)
4x (x - 1) - (x -1) (Factoring each pair of terms)
(x-1)(4x-1) (Factoring using the common factor)
So the answer would be:
(x + 5 )(x-1)(4x-1)