What is the value of m when -3 is one root of the equation: 3x^2 + mx + 3 = 0 Answer key: 10 Completing squares doesn't seem to work here and (0.5 * m)^2 is not applicable here, how to solve this? Thanks.
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Originally Posted by shenton What is the value of m when -3 is one root of the equation: 3x^2 + mx + 3 = 0 Answer key: 10 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: $\displaystyle 3(-3)^2-3m+3=0$ Thus: $\displaystyle 3(9)-3m+3=0$ Then: $\displaystyle 27-3m+3=0$ Therefore: $\displaystyle 30-3m=0$ Divide both sides by 3: $\displaystyle 10-m=0$ Add m to both sides: $\displaystyle \boxed{10=m}$
As usual, thanks for showing. Without gurus like you, I would have given up math.
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