When x takes a value, y has one and only one value corresponding to X. It can be drawn in a plane rectangular coordinate system.

When x=0, b is the point of the function on the y axis, and the coordinates are (0, b).

When b=0 (that is, y=kx), the linear function image becomes a proportional function, which is a special linear function. The image of the proportional function passes through the origin.

K (slope) = (Y2-y 1)/(X2-x1) (x1,y1,x2 and y2 are two coordinates respectively).

The product of slopes of two vertically intersecting lines is-1:k1* k2 =-1.

The slopes of two parallel straight lines are equal: k 1=k2.

When k>0, y increases with the increase of x;

When k < 0, y decreases with the increase of x.

Practice and graphics: Through the following three steps:

(1) list.

(2) tracking points; [Generally, two points are taken. According to the principle of "two points determine a straight line", it can also be called "two-point method". (3) Connecting lines can make images of linear functions-straight lines.