Graphing Lines

 The best way to learn about lines is to work with them without a calculator.  We are going to practice graphing lines by finding our own (x,y) values.  First, we will see how plugging in an “x” value will give you a “y” value.

Graphing Lines  Do the points (2,2) and (-3,5) line on the line: y = 3x – 4?  Plug in the “x” value and see if it equals the “y” value.  (2,2)  2 = 3(2) – 4  2 = 6 – 4  2 = 2  Yes, (2,2) lies on the line.  (-3,5)  5 = 3(-3) – 4  5 = -9 – 4  5 = -13  No, (-3,5) is not on the line.

Graphing Lines  To graph lines without a calculator, we will use a table.  We will pick the “x” values and plug them into the equation to get the “y” values.  How do we know what “x” values to pick?  I always use my favorites (-2, -1, 0, 1, 2) unless the equation has a fraction.  I will show you as we go!!

Graphing Lines  Graph y = 2x - 4 using a table. x2x – 4y -22(-2) – 4-8 2(-1) – (0) – (1) – (2) Plug in the “x” values to find the “y” values. 2.These are your ordered pairs. 3.Graph these points on the graph.

Graphing Lines  You can do this with any equation, not just lines.  Create a table and graph y = x 2 + 2x + 1. xx 2 + 2x + 1y -2(-2) 2 + 2(-2) + 11 (-1) 2 + 2(-1) (0) 2 + 2(0) (1) + 14