Answer:
An equation that can help Jerry to find the number of days he has been doing sit-ups is [tex]\frac{a_{n} -13}{2} +1 = n[/tex]
Step-by-step explanation:
First day = 13
Second day = first day + 2 = 13 +2 =15
Third day = second day + 2 = 17
Fourth day = Third day +2 = 19
So,
13 , 15 , 17, 19, 21, 23 ...........
The common difference is 2
By using arithmetic series
[tex]a_{n} = 13 + (n-1)d[/tex]
where
[tex]a_n[/tex] is the number of sit-ups done on the nth day
n is number of the days
d is the difference
Now
[tex]a_{n} = 13 + (n-1)(2)[/tex]
[tex]a_{n} -13 = (n-1)(2)[/tex]
[tex]\frac{a_{n} -13}{2} = (n-1)[/tex]
[tex]\frac{a_{n} -13}{2} +1 = n[/tex]
