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How to find the concavity?

Consider the function below.

C(x) = x^(1/3)(x + 4)

Only (1/3) is the exponent

1) find where the function is concave up and down

2) Find the intervals of increase and decrease

This question is seriously confusing me. I graphed this on Demos and then entered my answer and it's telling me it's wrong. Wolfram gives a different answer which is also wrong.

1 Answer

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  • ted s
    Lv 7
    6 years ago

    C(x) = x^(4/3) + 4 x^(1/3)....C ' = [4 / 3 ] x^(1/3) + [ 4 / 3 ] x^(-2/3)...

    C ' ' = [ 4 / 9 ] x^(- 2 / 3 ) - [ 8 / 9 ] x^(- 5 / 3 ) =

    [ 4 / 9 ] [ x^(- 2 / 3 ) ] [ x - 2 ] / x...x values to check are x = 0 , 2 for possible inflection values

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