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X, Y and Z coordinates

finding the midpoint of a line segment

  • find the average of the two x-coordinates, then do the same for the y-coordinates
  • these will be the coordinates of the midpoint

straight line graphs

horizontal and vertical lines: 'x = a' and 'y = a'

the main diagonals: 'y = x' and 'y = -x'

other sloping lines through the origin: 'y = ax' and 'y = -ax'

  • a tells you the steepness of the line
  • the bigger a is, the steeper the slope
  • a minus sign tells you it slopes downhill

plotting straight line graphs

the tables of 3 values method

  • choose 3 values of x and draw up a table
  • work out the corresponding y vlaues
  • plot the coordinates and draw the line

the x=0, y=0 method

  • set x = 0 in the equation, and find y - this where it crosses the y axis
  • set y = 0 in the equation and find x - this is where it crosses the x axis
  • plot these two points and join them up with a straight…


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