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The principle is very simple: if you are given two functions f1(x) and f2(x) as well as two coefficients c1 and c2, you certainly know how to compute the combination f(x) = c1f1(x) + c2f2(x).
And you know as well that to every function corresponds its graph. But on the graphical side, the addition of functions may appear harder, as you no longer have obvious means to compute.
This is precisely what this exercise proposes: you will be given graphs of functions, and asked to find back the coefficients of the combinations leading to these graphs. Like many other exercises on WIMS, training by this exercise will allow you to increase you ability to graphically recognize functions.
Please take note that WIMS pages are interactively generated; they are not ordinary HTML files. They must be used interactively ONLINE. It is useless for you to gather them through a robot program.