least-squares problem

lilme

Hello,

I'm stuck with a chemistry problem as I did not have any statistics course so far and don't really understand the explanations I found online.

It's about dating rock and I'm supposed to use the least-squares method to calculate the slope and intercept of a linear isochron.

I can solve the problem with any given pair of data, but my results differ quiet a lot when I try to use a least-squares method as described on different websites (so I probably don't understand it, which also shows as I don't quiet know what the result actually represents)

Here's a rather random set of data

x - y
700 - 17
40 - 2
100 - 3
150 - 4

further given:
slope m=e^(labda t) - 1
and
t=(1/labda)ln(m+1)
labda = 1.4x10^-11

Any help is greatly appreciated

lil'me

edit: I know that I get the slope as one result and can calculate the time with it. I also know how to calculate the intercept if y=mx+b and mx being the slope and b the intercept. I just don't know which figure to use for y.