Mathematics

Problem

For an arithmetic progression with first term

a

and common difference

d

and a geometric progression with the same first term

a

and common ratio

r

, the condition that their

k

th terms are equal is best expressed by which of the following equations? a)

a + k d = a r^{k-1}

a + (k-1)d = a r^{k}

a + (k-1)d = a r^{k-1}

a + (k-1)d = r^{k-1}