Y = ax 2+bx+c (a is not equal to 0)

Y = a (x-x 1) 2+y 1 (vertex, (x 1, y 1) is the vertex).

Y = a (x-x1) (x-X2) (x1,x2 is two intersections with the x axis).

In addition, the linear function y=kx+b(k is not equal to 0).

Then there is the proportional function y=kx(k is not equal to 0)

Inverse proportional function y=k/x(k is not equal to 0)

Then the problem of quadrant should be paid attention to in proportion, and nothing else should be paid.

I hope it helps you!