Respuesta :
Answer: -4
Step-by-step explanation:
p(x)=x^3+3x^2+ax-12
x+3 is factors means it divide completely so x=-3
p(-3)=(-3)^3+3(-3)^2+a(-3)-12
-27+27-3a-12=0
-3a-12=0
3a=-12
a=-12/3
a=-4
Answer: -4
Step-by-step explanation:
The most simple is
P(x)=x³+3x²+ax-12
P(-3)=0=(-3)³+3*(-3)²+a*(-3)-12=-3a-12
-3a-12=0
3a=-12
a=-4