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Mathematics 9 Online
OpenStudy (anonymous):

Can someone tell me how to find local maxima and minima! (Please)

OpenStudy (anonymous):

@ganeshie8

OpenStudy (anonymous):

@jim_thompson5910

jimthompson5910 (jim_thompson5910):

what's the function?

OpenStudy (anonymous):

No in general for any function

OpenStudy (anonymous):

Take any example

jimthompson5910 (jim_thompson5910):

well you would derive the function f(x) to get f ' (x)

jimthompson5910 (jim_thompson5910):

then set the derivative f ' (x) equal to zero and solve for x to get a list of critical values

jimthompson5910 (jim_thompson5910):

after you get a list of critical values, you have to use either the first derivative test or the second derivative test to see which critical value is a local min, local max, or a saddle point

OpenStudy (anonymous):

Ok so fo f(x) = 3t^2 - 4t f ' = 6t - 4 I set that = 0 6t -4 =0 t = 4/6 After that

jimthompson5910 (jim_thompson5910):

are you familiar with the first derivative test ?

OpenStudy (anonymous):

No actually i want to learn that

OpenStudy (anonymous):

I found out the first derivative

jimthompson5910 (jim_thompson5910):

ok

jimthompson5910 (jim_thompson5910):

draw out a number line and plot 4/6 on it |dw:1399867885598:dw|

jimthompson5910 (jim_thompson5910):

on either side of 4/6, plot a number so 0 is on the left for instance and 1 is on the right |dw:1399867921024:dw|

jimthompson5910 (jim_thompson5910):

if you were to plug x = 0 into the derivative function, you get ???

OpenStudy (anonymous):

-4

jimthompson5910 (jim_thompson5910):

so we get a negative result when you plug in a number to the left of 4/6 |dw:1399868565005:dw| We denote this with a negative sign circled above the interval (from negative infinity to 4/6)

jimthompson5910 (jim_thompson5910):

what happens when you plug in x = 1 ?

OpenStudy (anonymous):

2 Positive sign

jimthompson5910 (jim_thompson5910):

|dw:1399868844171:dw|

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