当0当0
当0令X2>X1 X2-X1=k (K>0)Y1=a^x1 Y2=a^x2 所以 y2-y1=a^x2- a^x1 =a^(x1+k)-a^x1=a^x1*a^k-a^x1=a^x1(a^k-1)因为 0