Question

What is the sum of the first 18 terms in the arithmetic sequence 3+7+11+...?

What are the coordinates of the point where the line y = -\frac{4}{5}x + 80 intersects the x -axis?

Answer 1

71

Explanation:

I am only able to really help with the first part of this question. I am very sorry about that!

Lets take a look at the sequence!

It starts with 3 and then goes to 7. Which means it is adding 4 each time it continues. To confirm this, lets look at 11. 7 goes to 11, which again means it is adding 4! So we understand and now the pattern!

Rather than doing a buttload of work, lets do it an easier way. Lets plug 18 into a calculator!

If you have one, all you need to do is add 3 plus 4. Then plus for again. That should start a ripple effect if you press enter. On the 18 term it would be 71!

Hope that helped.