When x ﹙ 40-x ﹚/2 = 180, X 1=20+2√ 10 (excluding), X2=20-2√ 10.

∴ Chicken farm area can reach 180m? ;

When x ﹙ 40-x ﹚/2 = 200, X 1=X2=20.

Can a chicken farm reach 200 meters? ;

(2) One side of the chicken farm (opposite to the wall) is x meters (0-x ≤ 25), and the other two sides are (40-x)/2m.

When x ﹙ 40-x ﹚/2 = 250, this equation has no solution.

∴ The chicken farm area can't reach 250 meters? .

3. Solution: Let the radius of the cylinder bottom be X㎝, which comes from the problem:

2πX？ +2πX 15=200π

X 1=5, X2=-20 (omitted)

A: The radius of the bottom of the cylinder is 5㎝.