When k>0, the straight line must pass through the first and third quadrants, and Y increases with the increase of X;

When k < 0, the straight line must pass through the second and fourth quadrants, and y decreases with the increase of x.

When y=kx+b:

while

k & gt0，b & gt0,

At this time, the image of the function passes through the first, second and third quadrants;

while

k & gt0，b & lt0,

At this time, the image of the function passes through the first, third and fourth quadrants;

while

k0，

At this time, the image of this function passes through the first, second and fourth quadrants;

while

k & lt0，b & lt0,

At this time, the image of this function passes through the second, third and fourth quadrants;

When b>0, the straight line must pass through the first and second quadrants;

When b<0, the straight line must pass through the third and fourth quadrants.

Particularly, when b=0, the image of the proportional function is represented by a straight line of the origin o (0 0,0).