# Math Help - 3x^2 + mx + 3 = 0, find the value of m

1. ## 3x^2 + mx + 3 = 0, find the value of m

What is the value of m when -3 is one root of the equation:

3x^2 + mx + 3 = 0

Completing squares doesn't seem to work here and (0.5 * m)^2 is not applicable here, how to solve this?

Thanks.

2. Originally Posted by shenton
What is the value of m when -3 is one root of the equation:

3x^2 + mx + 3 = 0

Completing squares doesn't seem to work here and (0.5 * m)^2 is not applicable here, how to solve this?

Thanks.
You know that: $3(-3)^2-3m+3=0$

Thus: $3(9)-3m+3=0$

Then: $27-3m+3=0$

Therefore: $30-3m=0$

Divide both sides by 3: $10-m=0$

Add m to both sides: $\boxed{10=m}$

3. As usual, thanks for showing. Without gurus like you, I would have given up math.