ah, so an aritmetic sequence can be written in form
![a_n=a_1+d(n-1)](https://img.qammunity.org/2019/formulas/mathematics/college/s34rkxq1wsiawvqq36bvorg3donx653lud.png)
where
is the nth term
is the first term
d is the common difference or how many times it increase or decreases each day
so an example:
Bob swims 2 miles on one day. Every day, he increases his distance by 0.2 miles. If he continues this pattern, how many miles will he swim on the 7th day?
![a_n=a_1+d(n-1)](https://img.qammunity.org/2019/formulas/mathematics/college/s34rkxq1wsiawvqq36bvorg3donx653lud.png)
![a_7=2+0.2(7-1)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/dn4ezpue5ghwuegytoihcv31e9l80ke4zx.png)
![a_7=2+0.2(6)](https://img.qammunity.org/2019/formulas/mathematics/middle-school/n76qvw0da1zmtxxe86tf448mp6s7dwiieh.png)
![a_7=2+1.2](https://img.qammunity.org/2019/formulas/mathematics/middle-school/q7yp1kggeq0khyns0zl4vfuzkfuwdeykma.png)
![a_7=3.2](https://img.qammunity.org/2019/formulas/mathematics/middle-school/e46nl6sowde198vng6el1udw09i0x9vj3j.png)
bob swims 3.2 miles on the 7th term
also, you can use f(n) instead of
![a_n](https://img.qammunity.org/2019/formulas/mathematics/college/fzb36m8zzqrub9yn2wh2sd3vqv3ujs174a.png)