The first equation (a)  is  .

This equation repreasents "Point-slope  form".

The second equation (b)  is  .

This equation repreasents "Slope-intercept  form".

The third equation (c)  is  .

This equation repreasents "Point-slope  form".

The fourth equation (d)  is  .

This equation repreasents "Standard form of a linear Ax+By=C form".

The first equation (a) is "Point-slope  form".

The second equation (b)  is "Slope-intercept  form".

The third equation (c)  is "Point-slope  form".

The fourth equation (d)  is "Standard form of a linear Ax+By=C form".