Question 832035: I have 3x^2+9x=0 and I have to solve it by first factoring out the common factor which ended up with 3x(x+3)=0, it then said to set each factor to zero, then put down what x equals, I don't know how to set each factor to 0.
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Answer by hovuquocan1997(83)   (Show Source):
You can put this solution on YOUR website! Well you get  and that's right, now only the "set factors to 0" confuses you right?
Factors are those terms that multiply together, and for solving equation, They mean "factor" are those terms that multiply together but those terms must involve an unknown variable, like x, y, z, a, b, c, etc
Let's talk about the problem
Let's talk about the right side
3x(x+3)
What are the terms that multiply together in this side?
They are 3, x, and x+3 right? Since you have 3 times x times (x+3) give you 3x(x+3)
So you have 3 factors, but remember, in solving equation, we only take factors that involve unknown variable, that means we throw the 3 away, we only take x and x+3
Now let's "set each factor equal 0"
 and 
and 
So your solutions are 0 and -3
TA-DAH
:D
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