1. The Graphs of Quadratic Equations
Sunday, 17 February 2019
The Graphs of Quadratic Equations
A quadratic equation is an equation that has a x2 value.
All of these are quadratics:
y = x2
y = x2 + 2
y = x2 + x – 4
y = x2 + 2x – 3
So quadratic means that there must be a x2 in what ever y equals

2. If you were asked to draw the graph of y = x2 + 2, follow these steps
1) Draw a chart putting in the x values from –4 to +4 x -4 -3 -2 -1 1 2 3 4
The exam writer will probably do this for you

3. If you were asked to draw the graph of y = x2 + 2, follow these steps
2) Calculate x2 and put these values into the table. Notice that all of these are positive x -4 -3 -2 -1 1 2 3 4 x2 16 9
The values are always positive because a minus time a minus is a plus -3 X –3 = 9 etc.

4. If you were asked to draw the graph of y = x2 + 2, follow these steps
3) Add the 2 onto the x2 and put these values into the table. x -4 -3 -2 -1 1 2 3 4 x2 16 9
x2 + 2 18 11 6

5. All you need to do now is to plot the x number against the y number.
If you were asked to draw the graph of y = x2 + 2, follow these steps
4) You have done all that the equation asks so you will have the y value. x -4 -3 -2 -1 1 2 3 4 x2 16 9
x2 + 2 18 11 6 y
All you need to do now is to plot the x number against the y number.

6. x -4 -3 -2 -1 1 2 3 4 x2 16 9
x2 + 2 18 11 6 y

7. The exam writer will probably do this for you
If you were asked to draw the graph of y = x2 + x – 4, follow these steps
1) Draw a chart putting in the x values from –4 to +4 x -4 -3 -2 -1 1 2 3 4
The exam writer will probably do this for you

8. If you were asked to draw the graph of y = x2 +x – 4, follow these steps
2) Calculate x2 and put these values into the table. Notice that all of these are positive x -4 -3 -2 -1 1 2 3 4 x2 16 9
The values are always positive because a minus time a minus is a plus -3 X –3 = 9 etc.

9. If you were asked to draw the graph of y = x2 + x – 4, follow these steps
3) Add the x onto the x2 and put these values into the table. x -4 -3 -2 -1 1 2 3 4 x2 16 9
x2 +x 12 6 20

10. If you were asked to draw the graph of y = x2 + x – 4, follow these steps
3) Subtract 4 from these values to obtain x2 + x – 4. x -4 -3 -2 -1 1 2 3 4 x2 16 9
x2 +x 12 6 20
x2 + x – 4 8

11. All you need to do now is to plot the x number against the y number
If you were asked to draw the graph of y = x2 + x – 4, follow these steps
3)You have done all the equation asks so you must have the y value. x -4 -3 -2 -1 1 2 3 4 x2 16 9
x2 +x 12 6 20
x2 + x – 4 8 y
All you need to do now is to plot the x number against the y number

12. x -4 -3 -2 -1 1 2 3 4 x2 16 9
x2 +x 12 6 20
x2 + x – 4 8 y