Sentence:  Let us take any point of the first <WSD>graph</WSD>, for example, \textstyle x=\frac 1 2, y=\frac 4 5, that is, the point \textstyle M_1(\frac 1 2,\frac 4 5). 
Meaning of the word marked with <WSD> tags:  A set of points constituting a graphical representation of a real function;  a set of tuples (x_1, x_2, \ldots, x_m, y)\in\R^{m+1}, where y=f(x_1, x_2, \ldots, x_m) for a given function f: \R^m\rightarrow\R.