Problem 16. Show that 1+2+4+...+26(n-1)=2^(n)-1 I first decided to use the formula: a_n=a_1*r^(n-1) Problem24. Find the sum of the series 1-3+5-7+9-11+....+1001. Problem 26. Suppose a doctor earns $40,000 during the first year of practice. Suppose also that each succeeding year the salary increases 10%. What is the total of the doctor's salaries over the first 10 years? How many years must the doctor work if the salary total is to exceed a million dollars?