Question

Help me please....

Question
Three sides of a rectangular paddock are to be fenced, the fourth side being an existing straight
water drain. If 1000 m of fencing is available, what dimensions should be used for the paddock so
that it encloses the maximum possible area?

Answer 1

A=x(1000-2x)
A=1000x-2x²
take the first derivative of A and set equal to zero
A'=1000-4x
1000-4x=0
4x=1000
x=250
the paddock should be 250 by 500