In the second year, the growth rate of fish was 200%*( 1/2)= 100%.

In the third year, the growth rate of fish is 200% * (1/2) 2 = 50%.

In the fourth year, the growth rate of fish is 200% * (1/2) 3 = 25%.

In the fifth year, the growth rate of fish is 200% * (1/2) 4 =12.5%.

After four years of feeding, the weight of fish is expected to be the same.

(100%+200%) (100%+100%) (100%+50%) (100%+25% = () times.

(1) After feeding for 5 years, the fish weight is expected to be the original.

( 100%+200%) ( 100%+ 100%) ( 100%+50%) ( 100%+25%).

The general formula is f1= (1+a) (1+ab) (1+a * B2) ... [1+a * b (c-1)]

Where a=200%, b= 1/2 (half) and c=5 (year).

(2) the general formula is F2 =1+a * b (c-1)-d.

Where a=200%, b= 1/2 (half), d= 10%,

When c=5 (year) f2= 1.025,

When c=6 (year) f2=0.9625 (less than 1 at first), i.e.

After six years, the total weight began to decrease.