erza is training for a track race. He starts by sprinting 100 yards. he gradually increases his distance, adding 5 yards a day for 21 days. Which explicit formula models this situation? A. an=100 + (n-1)21 B. an=100 + (n-1)5 C. an=5 + (n-1)100 D. an=21 + (n-1)5

B. an=100 + (n-1)5

Step-by-step explanation:

Using the explicit formula

an = a1+ d(n-1)

we know a1 is 100, which is the staring amount

We know d is the amount added each time or the common difference which is 5

an = 100 + 5(n-1)

If we want to find a specific day, we can substitute in for n

step-by-step explanation:

descending order means to order the polynomials from the term with the largest exponent to the term with the smallest exponent.  

therefore, the correct answer is d.