SOLUTION: if x=-3 is a root of the equation {{{x^3+3x^2-ax-12=0}}}, what is the value of a

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Question 378790: if x=-3 is a root of the equation x%5E3%2B3x%5E2-ax-12=0, what is the value of a
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E3%2B3x%5E2-ax-12=0,
x=-3
plug the value of x
(-3)^3+3(-3)^2-a(-3)-12=0
-27+27+3a-12=0
3a-12=0
+12
3a=12
/3
a=4
...
m.ananth@hotmail.ca