If x + 3 is a factor of x3+3x2+ax−12, what is the value of a?

  -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

-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

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