Limitations of linear equations

Limitations of various linear equations;

(1) point inclination and inclination cannot represent a straight line without slope;

(2) Two-point formula cannot represent a straight line parallel to the coordinate axis;

(3) Intercept formula cannot represent a straight line parallel to the coordinate axis or passing through the origin;

(4) The coefficients A and B in the general formula of linear equation cannot be zero at the same time.