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Help with arithmetic sequence problem

  • #1
The zeros of the polynomial f(x) = x^3 - 33x^2 + 354x + k form an arithmetic sequence. What is the value of k?

so i let the zeros = a, b, and c. then i did b - a = c - b since it's an arithmetic sequence and they have common differences. so now i have a + c = 2b. i don't know what to do from here. help is much appreciated!
 

Answers and Replies

  • #2
symbolipoint
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Maybe you want four equations because you have four unknowns; although maybe you really have three unknowns (a, b, and k, since you determined c=(2b-a) ).

(x - a)(x - b)(x - (2b-a)) = x^3 - 33x^2 + 354x + k = 0

Could you use this, multiply the lefthand side, and then equate the coefficients?
 
  • #3
oh i see.
it took a while to multiply out the expression, but i got the answer.
thanks! :)
 

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