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Which of the following is a polynomial with roots  square root of 5, square root of 5, and 3 ? x3  2x2  3x + 6, x3 + 2x2  3x  6, x3  3x2  5x + 15, or x3 + 3x2  5x  15?
 one year ago
 one year ago
Which of the following is a polynomial with roots  square root of 5, square root of 5, and 3 ? x3  2x2  3x + 6, x3 + 2x2  3x  6, x3  3x2  5x + 15, or x3 + 3x2  5x  15?
 one year ago
 one year ago

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tcarroll010Best ResponseYou've already chosen the best response.1
If you have roots of: a, b, and c your polynomial has the form: (x  a)(x  b)(x  c) = 0 Substitute a, b, and c for the given roots and multiply the expression out on the left side.
 one year ago

DeadShotBest ResponseYou've already chosen the best response.0
x^3 2.25x^2+2.25x^23x22.25x+2.25x3x15
 one year ago

DeadShotBest ResponseYou've already chosen the best response.0
simplified, it's x^33x^23x15, right?
 one year ago

tcarroll010Best ResponseYou've already chosen the best response.1
You wouldn't even have to ask that last question because you have 4 choices and this choice is not even listed among them. Here's a hint on how to expand that expression I gave you: (x  a)(x  b)(x  c) = 0 [(x  a)(x  b)](x  c) = 0 [x^2  (a + b)x + ab](x  c) = 0 [x^2  (a + b)x + ab]x  [x^2  (a + b)x + ab]c = 0
 one year ago

DeadShotBest ResponseYou've already chosen the best response.0
[x^2(2.25+2.25)x + (2.25)*2.25]x[x^2(2.25+2.25)x + (2.25)*2.25]3=0
 one year ago

tcarroll010Best ResponseYou've already chosen the best response.1
Where are you getting +2.25 from? Neither has anything to do with sqrt(5).
 one year ago

DeadShotBest ResponseYou've already chosen the best response.0
sqrt(5) is approx 2.25
 one year ago

tcarroll010Best ResponseYou've already chosen the best response.1
You don't want to be working with approximations here.
 one year ago

tcarroll010Best ResponseYou've already chosen the best response.1
I would suggest evaluating the following first: [x  sqrt(5)][x + sqrt(5)] That correspond to the leftmost factors. Get that down to a trinomial.
 one year ago

DeadShotBest ResponseYou've already chosen the best response.0
(x^25) (x3)=x^3  3x^2  5x + 15
 one year ago

tcarroll010Best ResponseYou've already chosen the best response.1
The third root is "3", so you have: [x  (3)] or (x + 3) for that third factor. I think that's where you having your trouble. When you subtract a negative, it's like adding a positive.
 one year ago

tcarroll010Best ResponseYou've already chosen the best response.1
So, taking up from where you were writing: (x^2  5)(x + 3) = 0 And then expand that. You are very close to your answer now.
 one year ago

DeadShotBest ResponseYou've already chosen the best response.0
so, it's x^3+3x^25x15?
 one year ago

tcarroll010Best ResponseYou've already chosen the best response.1
Yes! Excellent! Just remember about subtracting negatives and you will be ok.
 one year ago

DeadShotBest ResponseYou've already chosen the best response.0
Okay, Thanks for the help!
 one year ago

tcarroll010Best ResponseYou've already chosen the best response.1
You're welcome! Good luck to you in all of your studies and thx for the recognition! @DeadShot
 one year ago
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