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    Equation of a Line... HELP!!!!!! hamzamughees

    There are three different formulae for the equation of a line

    y= mx + x

    y - y1 = m(x - x1)

    ax + by + c = 0

    Which one is easier and works all the time.

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      my teacher says you need to learn all three i get so mixed up on these too!!

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      Which one do you think is easiest though?

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      it depends on the question given but in my opinion i find ax+by+c=0 easy

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      youre welcome

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      i've never learnt ax+by+c =0 and still got A in jc maths, and the fist and second formulae are just variations on each other so you only need to learn the y-y1=m(x-x1), however ironically you don't need to learn any of these as they are in the formula book.

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      but how would you know which one to use then? @chris241197

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      it says in the formula book what you use them for

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      ok thanks

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      When I learned these formulae my teacher said that each of these equations are better in some occasions.

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      im so confused like how do you know when reading a question which formula you use?

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      ughhh so confusing haha

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      Roberto Mane

      It usually tells you in the question,like in an area and volume question where it tells you to express your answer in terms of pi.

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      oh ok thanks

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      y= mx + x

      should be

      y= mx + c

      Eamonn -

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      Oh yea I noticed that later

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      Sorry my bad and thanx

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      y=mx+c gives you the slope (m, rises/run) and the y intercept.

      this equation is easiest to work with, makes graphing easier and can be worked out from a well drawn graph.

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      y - y1 = m(x - x1)

      is used if you have the slope of the line and the coordinates of a point on the line. If you know these, you can sub them in to find out the equation of the line.

      And if you don't know the slope, but have 2 points, then there is a formula to find the slope of the line between those points, so do that first, then use the above formula to find the equation of the line.

      Eamonn -

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      As for

      ax + by + c = 0

      This form is not as easy to interpret as y = mx + c

      You could extract some info about the slope and the y intercept e.g. the slope would be -a/b, and the y intercept is -c/b in this case.

      But you might find it easier to rearrange whatever equation you are given, so as to put it in the form y=mx+c. In doing so, you need to be careful to change the sign of any term you bring across the = sign, and also if you divide one term, you must divide them all by the same.

      Once in the form y = mx + c, it's easy to interpret.

      Eamonn -

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      thank you so much guys.

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