Determine the absolute extreme values of f(x)=4√x -2x on the interval [1,4]

I found the derivative of f(x)=4√x -2x

f'(x)=2/x^(1/2) - 2

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I have no idea what to do now.

1 answer

Since you have found your derivative you then need to move on and find its critical values(where the derivative equals zero). Then if those numbers are within the interval [1,4] you must also plug those into your orignal function. If they do not, then they should be disreguarded and thrown out

F(1)= 2/(1^(1/2)-2=0 giving you the point (1,0) which is your max

F(4)= plug the 4 into your x value for your derivative and you should get -1