Thread: How to get demand equation

Hello,

it's probably a silly question for you, but I'm stuck.

It's simple. There's given a table of prices and quantities and I need to get a demand equation from it. I know the answer, but I would like to know the 'HOW-TO'.

Q ‖ 1 ‖ 2 ‖ 3 ‖ 4 ‖ 5 ‖ 6 ‖ 7 ‖
P ‖ 35‖30‖25 ‖20‖15‖10‖ 5 ‖

Answer: Q = 80 - 2P.

What's on my mind: I understand we can calculate the slope, which is -1/5 and then we should do something I don't know ( well I've read that we can put the slope to p=mx+b and solve it, but it didn't give me the right answer). Also it can be found using matrix algebra, which I'm curious about.

Thanks in advance.

My bad. I've managed to make a mistake with the slope. The thread can be deleted.