SOLUTION: Hi, I've already done a few of these problems in the past, but this time I was confused on one of the steps.The question is "True or false? 2r3 + 3r2 − 18r − 27 = 0 ha

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Hi, I've already done a few of these problems in the past, but this time I was confused on one of the steps.The question is "True or false? 2r3 + 3r2 − 18r − 27 = 0 ha      Log On


   

Question 738044: Hi,
I've already done a few of these problems in the past, but this time I was confused on one of the steps.The question is "True or false? 2r3 + 3r2 − 18r − 27 = 0 has solutions 3, -3, and 3/2."
So far, I have (2*3)squared, plus 3r squared, minus 18*3/2. I don't know how to simplify the 3r squared part though. Could you help?Thanks(:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
"True or false? 2r3 + 3r2 − 18r − 27 = 0 has solutions 3, -3, and 3/2."
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f%28r%29+=+2r%5E3+%2B+3r%5E2+-+18r+-+27
f(3) = 54 + 27 - 54 - 27 = 0
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f(-3) = -54 + 27 + 54 - 27 = 0
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f(3/2) = 27/4 + 27/4 - 27 - 27 = -81/2
Not a zero --> false
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