
Trial and Error only ?
Hi ! I'm trying to solve this problem. Though I get around to solving it by trial and error. The answer btw is 4.61 % ... But I am wondering ... Can this problem be solved other than trial and error method ?
Problem:
A piece of machinery can be bought for $10,000 cash, or for $2,000 downpayment and payments of $750 per year for 15 years. What is the annual interest rate for the time payments ?

Only by trial/error; known as "numerical solution":
suggest you google "numerical solution" ; or "iteration".