(1)利润函数y＝f(x)
=R（x）-G(x)
＝3000x-20x^2-500x+4000
=-20x^2+2500x+4000
y=F(x)
=f(x+1)-f(x)
=-20(x+1)^2+2500(x+1)+4000-(-20x^2+2500x+4000)
=-40x+2480
(2) 利润函数y＝f(x)
=-20x^2+2500x+4000
当x=-2500/(-20*2)=125/2时取最大值118125
y=F(x) =-40x+2480当x=0时取最大值2480
所以没有相等的最大值