In +b, when b=0, it is a proportional function. So the proportional function y=kx

Is a linear function y=kx.

A special case of+b.

Their nature is * * *:

1. Its image is a straight line.

2. When k > 0, y increases with the increase of x; When k < 0, y decreases with the increase of x.

The difference is that the image of the proportional function must pass through the origin. Linear function y=kx

+b image, when b≠0, but the origin.