f(x) = 3x+x^3,  x is bigger than 0

  1. Differentiate to find  f ‘ (x)



Given that f ‘ (x) = 15

  1. Find the values of x



11) The curve c has an equation Y = kx^3 -x^2 +x-5 where k is a constant find dy/dx

asked Nov 1, 2011 in Algebra 1 Answers by anar1995 (480 points)

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1 Answer

10. f'(x)=3+3x^2=15; x^2=(1/3)(15-3)=4, so x=-2 or 2. But if x>0, x=2 is the solution.

11. dy/dx=3kx^2-2x+1
answered Dec 16, 2015 by Rod Top Rated User (588,020 points)
Answer my questions plz! I got a 1 hour time limit on it.

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