Question

(2-3乘5负一次方）+（2的2次方-3乘5的负二次方）+（2的n次方-3乘5的负n次方）的值

过程

Answer 1

(2-3*5^-1)+(2^2-3*5^-2)+…+(2^n-3*5^-n)=2+2^2+…+2^n-3*(5^-1+5^-2+…5^-n)
=2*(2^n-1)/(2-1)-3*5^-1*(1-5^-n)/(1-5^-1)
=2*(2^n-1)-3/4*(1-5^-n)
=2^(n+1)+3/(4*5^n)-11/4