Graphing Lines

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.

x 2x – 4 y

-2 2(-2) – 4 -8

-1 2(-1) – 4 -6

0 2(0) – 4 -4

1 2(1) – 4 -2

2 2(2) - 4 0

1. 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 = x2 + 2x +

1.x x2 + 2x + 1 y

-2 (-2)2 + 2(-2) + 1 1

-1 (-1)2 + 2(-1) + 1 0

0 (0)2 + 2(0) + 1 1

1 12 + 2(1) + 1 4