Coordinate systems, linear functions
-Each function can be plotted in a coordinate system.
-The best known coordinate system is the cartesian one, named after Descartes.
-This kind of coordinate sytem consists of two mutually perpendicular coordinate axes whose intersection point is called the origin.
-The vertical axis is called the y-axis while the horizontal axis is called the x-axis.
-The coordinate system divides the plane into four equal quadrants.
-Every point of the plane can be represented by its coordinates.
-Coordinates are used to mark the points.
-A point is given int he form of P(x;y). The value of x always comes first.
-Def.: lett he function f:A→B, f(x)=mx+b (m and b are constants) be given. The function f is called a linear function.
-if m=0 then the function f(x)=b is a straight line which is perpendicular to the y-axis (or parallel with x-axis)
A special case of linear functions is f(x)=mx. It is called a function of direct proportionality. The graph of f(x)=mx is a straight line which passes through the origin.
Any function whose graph is a straight line is called a linear function. They are also called the functions of the first degree.
In function f(x)=mx+b m is called a gradient (which can be either positive or negative), b is called an intercept of the y-axis.
To draw a straight line graph only two points need to be known. Once these have been plotted, the line can be drawn between them and extended if necessary of both ends.
2012.03.02.