When plotting the graph of a quadratic equation, it's useful to draw out and complete a table so that we can find our co-ordinates to plot.
The x values are fixed and the corresponding y values are calculated.
Complete the following graph table:
In the table above the x values range from -3 to +3.
To calculate our values for the y co-ordinates we need to substitute the given values of x into the equation for the quadratic curve.
Likewise, if we are given the y co-ordinates we can substitute these values into the equation and solve.
A = x2 when x = -1
Therefore, A = (-1)2 = 1
B = 1 - 2 = -1
C = 0 - 2 = -2
D = x2 when x = 1 so D = (1)2 = 1
E = 4 - 2 = 2
F = -2 like the rest of that row
G = x2 - 2 when x = 3 so G = (3)2 - 2 = 9 - 2 = 7
Let's consolidate this knowledge by working through some questions together.