can someone give me an example of how can one apply any concept (determining the slope and equation of a line, applying linear functions to mathematic applications, solving equations using the method of least squares) in order to decide if data are linear.
Since this is not my area of expertise, I searched Google under the key words "slope equation line" to get these possible sources:
http://www.wtamu.edu/academic/anns/mps/math/mathlab/int_algebra/int_alg_tut15_slope.htm
http://www.purplemath.com/modules/slope.htm
http://id.mind.net/~zona/mmts/functionInstitute/linearFunctions/lsif.html
http://www.mathwords.com/p/point_slope_equation_of_a_line.htm
http://en.wikipedia.org/wiki/Slope
You can find the remaining information you desire, if you use appropriate key words to do your own search.
I hope this helps. Thanks for asking.