please help meeee!!!

Question

What is the 50th term of the sequence below?

9, 5, 1, -3, …

Answer 1

nth term of an arithmetic sequence an = a1 + (n-1) * d, where a1 is the first term, n is the number of terms and d is the difference between terms.

Here the constant difference(d) between terms is -4, a1 = 9 and n = 50 so

a(5) = 9 + (50-1)-4 = 9 + 49*-4 = -187

Answer 2

Hello, Christina,

The sequence decreases by 4 each step. You can build a table of all 50 in the sequesnce, subtracting 4 from the previous value in each step. Or you can make an equation that will do the work for you.

We can set x equal to the step number, starting with x = 1. Y will be the value of the number in that sequence.

For x = 1, y= 9.

For x = 2, y = 5

We could say that y = 9 -(x-1)*(-4), or y=9-(2-1)*(4)

y = 9-4, or 5

The (x-1) expression says take the sequence step, x, and subtract 1 so that we account for the fact that we started with 9, so we don't subtract 4 from the starting number (when x=1).

For x = 3, we would get 9-(3-1)*4, or 9-8 = 1

For x = 4, we get y = -3

And so on.

For x=50, y = 9-(50-1)*4

y = 9-(49)*(4)

y = -187

Bob