Question

The formula to find a certain number in an arithmetic sequence is an=a1+d(n−1) .

Solve for n.

Answer 1

an = a1 + d(n−1)

an = a1 + dn - d

dn = an - a1 + d

n = (an - a1 + d) / d

n = (an - a1)/d + 1

Answer is B.

n = (an - a1)/d + 1