Question

witch rule can you use to find the nth term of an arithmetic sequence in witch the common difference is 5 and a12=63

Answer 1

Any arithmetic sequence can be expressed as:

a(n)=a+d(n-1), a=initial term, d=common difference, n=term number

We are only told that d=5 and a(12)=63 so:

53=a+5(12-1)

53=a+60-5

53=a+55

a=-2  now we have solved for a and we can say:

a(n)=-2+5(n-1)  which neatened up....

a(n)=-2+5n-5

a(n)=5n-7

The above is the rule to find the value of the nth term.