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Completing the Square

Exercise given in textbook:

A farmer has 40m of fencing with which to enclose a rectangular pen.Given that the pen is x m wide -

show that it's area is (20x - x^2)m^2

and deduce that the maximum area that he can enclose (Answer given 100m^2).

I have completed lots and lots of exercises involving completing the square- also with minimum and maximum values but am obviously missing something here.

Thank you.

Solution Preview

Hi, here is the solution.

Area = 20x -x^2

Find the derivative and set equal to zero.

dA/dx = 20-2x

dA/dx=0 => 20-2x=0

x= ...

Solution Summary

A quadratic equations word problem is solved by completing the square. The solution is detailed and well presented. The response was given a rating of "5/5" by the student who originally posted the question.