Finding Derivitive of a Triangle Area

[odolwa99]

My answer to this question seems close to that of the book but I have only solved for +1/2 and not the -1/2. Can anyone help?
Many thanks.

Homework Statement

Q. The area of a triangle is \frac{-4m^2 + 4m - 1}{m}. Find the value of m via differentiation.

Homework Equations

The Attempt at a Solution

Attempt: \frac{dA}{dm} = \frac{4m^2 - 4m - 1}{m^2} = 0 => 4m² - 4m + 1 = 0 => (2m - 1)(2m - 1) => m = 1/2

Ans.: (From textbook): \frac{dA}{dm} = \frac{-4m^2 + 1}{m^2} = 0 => m = +/- 1/2

 

[Pengwuino]

The question makes no sense and sounds incomplete. Find m by differentiation? That's not the derivative of A either. Are you sure you're not missing a portion of the problem?