Posted by **Alannah** on Monday, December 3, 2012 at 11:33am.

for f(x= -1/4x4-1/3x3+2x, use analytic method to find the exact intervals on which the function is a)increasing, b)decreasing, c)concave up, d)concave down, then find any e)local extreme values, f)inflection points

- grade 12 AP calculus -
**Steve**, Monday, December 3, 2012 at 12:21pm
y = -1/4 x^4 - 1/3 x^3 + 2x

y' = -x^3 - x^2 + 2

y'' = -3x^2 - 2x

inflection where y''=0: x=0, -2/3

local extrema where y'=0 and y''≠0: x=1

increasing where y'>0: x<1

decreasing where y'<0: x>1

concave up where y''>0: -2/3 < x < 0

concave down elsewhere

- grade 12 AP calculus -
**Alannah**, Tuesday, December 4, 2012 at 11:02pm
how did you factor y' for this question?

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