Find the maximum and minimum values of the function y = x − 1/ x^2 + 80x on the interval [1,81]

Answer 1

y = 81x-x^-2 ,,, y' = 81+2x^-3 =0 @x=3.43. Since y''(3.43)< a local Maximum exists at x=3.43. y(1)=0 and y(81)=6482 the Max and Min values are 6482 and 0 respectively