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rach_ell
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The function f(x)= kx^3  8x^2 x + 3k + 1 has a zero when x=2. Determine the value of k. Graph f(x) and determine all the zeros. Then rewrite in factored form.
I found that k=3 so far, but I'm not sure how to graph it without making a table of values, or how to find the zeros. Any ideas?
 11 months ago
 11 months ago
rach_ell Group Title
The function f(x)= kx^3  8x^2 x + 3k + 1 has a zero when x=2. Determine the value of k. Graph f(x) and determine all the zeros. Then rewrite in factored form. I found that k=3 so far, but I'm not sure how to graph it without making a table of values, or how to find the zeros. Any ideas?
 11 months ago
 11 months ago

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myininaya Group TitleBest ResponseYou've already chosen the best response.1
So f is 0 when x=2 So write this f(2)=0 except actually evaluate the function given at x=2 Replace all of those x's with 2 and then set that result to 0.
 11 months ago

rach_ell Group TitleBest ResponseYou've already chosen the best response.0
I did that already to find the k value (3), but I'm stuck on the graphing part. And also on how to find the zeros.
 11 months ago

myininaya Group TitleBest ResponseYou've already chosen the best response.1
Do you know synthetic division?
 11 months ago

rach_ell Group TitleBest ResponseYou've already chosen the best response.0
We haven't learned that yet
 11 months ago

myininaya Group TitleBest ResponseYou've already chosen the best response.1
Do you know long division then?
 11 months ago

myininaya Group TitleBest ResponseYou've already chosen the best response.1
Great. Since x=2 is a zero, then x2 is a factor of 3x^38x^2x+9+1
 11 months ago

myininaya Group TitleBest ResponseYou've already chosen the best response.1
See what another factor is by seeing how many times x2 goes into 3x^38x^2x+10
 11 months ago

myininaya Group TitleBest ResponseYou've already chosen the best response.1
I must leave but you should get a quotient and no remainder. You should be able to factor the quotient. You should be able to now find your 3 zeros. Test the intervals between and before and after each zero to see if the function is above or below the xaxis. Then connect the dots.
 11 months ago

rach_ell Group TitleBest ResponseYou've already chosen the best response.0
Thank you, I will try that!
 11 months ago
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