Decide whether you want to create a function for an upward parabola or a downward parabola. An upward parabola is u-shaped and requires the "a" in your quadratic function to be a positive number. If your "a" is negative, your function will be represented by a downward parabola that is n-shaped. Choose a positive or negative number for "a" and write it down for later.
Use your ruler to draw the axes of a graph. Draw a horizontal line for the x-axis on your graph paper. Label the x-axis in numerical order with both positive and negative numbers. The center point of the x-axis should be 0, with positive numbers to the right of 0 and negative numbers to the left.
Using your ruler, draw a vertical line to represent the y-axis of the graph. The y-axis should intersect the x-axis at the center point of 0. Label the y-axis in numerical order with positive numbers above the x-axis and negative numbers below it.
Choose two points on the x-axis where your parabola will intersect. Select the point that is to the left of your other chosen point. Write down the corresponding number on the x-axis. You will use this number as the "b" in your quadratic function.
Select the remaining point you chose on the x-axis and write down the corresponding number. This will be the "c" in your function.
Substitute the numbers you wrote down for a, b and c into the formula f(x) = ax^2+bx+c to create your function. For example, if you chose a=2, b=-3 and c=5, your function will be f(x) = 2x^2-3x+5 and it will be represented by a u-shaped parabola.