#3 pre-calculus: approximate interval where y is decreasing

greenblunts

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Jul 19, 2006
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Use a graphing calculator to approximate to three decimal places the interval(s) where the function is decreasing. Use (open) interval notation.
y = 0.2 x^5 - 0.7313 x^4 - 4.2021 x^3 - 4.3875 x^2 - 46.8187 x + 2.08

i have no idea how to get approximate answers.PLEASE HELP!
 
Use a graphing calculator to approximate to three decimal places the interval(s) where the function is decreasing. Use (open) interval notation.
y = 0.2 x^5 - 0.7313 x^4 - 4.2021 x^3 - 4.3875 x^2 - 46.8187 x + 2.08

i have no idea how to get approximate answers.PLEASE HELP!

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You will have to graph the function. I found a window of -20<x<+20 and -800<y<+300 works.

Next, you will have to find the "local maximum" and "local minimum" of the graph using the features of your calculator. On the TI-83, this is in the "2nd CALC" menu, #3 and #4. The function is decreasing between the local max and the local min. The calculator can be set to give the required number of decimal places.

Hope that helps...

Steve
 
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