A biologist begins working with a sample containing 20,000 bacteria. The population size doubles every 10 days according to the equation p(t)=20,000(2)^t/10, where t represents the number of days. After seven days the biologist begins working with a second sample of 20,000 bacteria. The equation used to represent the population of sample 2 after t days is p(t)=20,000(2)^t-7/10. Which of the following is an equivalent form of the equation for the population of sample 2?