Exercise 5 Page 691

Explicit equations for the nth term of an arithmetic sequence follow a certain format. a_n= a_1+( n-1) d In this form, a_1 is the first term in the sequence, d is the common difference, and n is the position of the desired term in the sequence. We are given that a_1= 10 and d= - 5, so we can substitute these values to write our equation. a_n= 10+( n-1) (- 5) Let's also simplify this equation.

To find the value of the 9th term, we substitute n= 9 into this equation and solve for a_9.

The 9th term in the sequence is - 30.