Question

Please help I have no idea what to do!

Find an equation for the nth term of the arithmetic sequence.

a19 = -58, a21 = -164

Answer 1

So the formula for the nth term in an arithmetic sequence is: Un = a + d(n-1)

Answer 2

Where n = the value of the term you are trying to find.

Answer 3

so I solve for n?

Answer 4

No, you find the difference between each term (d in the formula above) and the first term of the arithmetic sequence (a in the formula above)

Answer 5

so -58+164? finding the difference?

Answer 6

The common difference is (-164+58)/2. Which equals -53

Answer 7

So the answer is an = 896 - 53(n - 1)
?

Answer 8

Yes and your teacher/tutor might expect you to expand those brackets to make it: Un = 896 -53n +53 = 949 - 53n

Answer 9

But both would be correct.

Answer 10

you are great!!!!

Answer 11

:)