# linear relation W=mA+c

#### thatsnotalion

Hi i need help with this question.

i need to show that the data fit closely with the linear relation W=mA+c, and determine the constants m and c?

the data in the table is as follows:

A: 20, 22, 30, 34, 42, 43, 46, 54, 56, 68, 70
W:0.08, 0.10, 0.15, 0.20, 0.27, 0.26, 0.31, 0.36, 0.40, 0.49, 0.49

#### pickslides

MHF Helper
Do you have a copy of MS excel, a graphical calculator or any other software that can do this for you?

M guess is... $$\displaystyle W = 0.0085A - 0.0905$$

Last edited:

#### thatsnotalion

how id you guess that? and no, i don't have any programs to help.

do i use simultaneous eqns?
for example
0.08=20m+c
0.10=22m+c

#### pickslides

MHF Helper
do i use simultaneous eqns?
for example
0.08=20m+c
0.10=22m+c
You can do that. But don't pick to points so close to each other. You really should plot the points first then draw a line through the points for a best fit (make sure there is an even amount of points above and below the your line. Then pick points that are close to and at either end of the line.

I have made an edit above. (Happy)(Rofl)

#### thatsnotalion

hmm thanks! i'm still a little unsure though =/

#### pickslides

MHF Helper
Try solving.

$$\displaystyle 0.08=20m+c$$
$$\displaystyle 0.49=70m+c$$

Do you know how?

#### thatsnotalion

i used elimintation and got c=-0.084, m=0.0082?

#### pickslides

MHF Helper
i used elimintation and got c=-0.084, m=0.0082?
So did I. Well done!

#### thatsnotalion

awesomesauce. thanks for that!