How can programmers build on abstractions to create further abstractions?

Least square fit to polynomial write a function leastsquarefit3pol that solves a linear system of equations to find a least squares fit of a third order polynomial to an experimental data set given as two row arrays. the function leastsquarefit3pol must explicitly solve a set of linear equations and cannot use polyfit. there should be no restriction on the size of the problem that can be solved.

Jennifer has to set up a network in a factory with an environment that has a lot of electrical interference. which cable would she prefer to use? jennifer would prefer to use because its metal sheath reduces interference.

Plz ( which is an example of a good url?