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Solving Quadratic Equations

Solving Quadratic Equations 1.11 - Solution

arrow_back Return to Solving Quadratic Equations

We have a quadratic equation, written in standard form. To draw the graph of the related quadratic function we must start by identifying the values of and We can see that and Now, we will follow four steps to graph the function.

  1. Find the axis of symmetry.
  2. Calculate the vertex.
  3. Identify the intercept and its reflection across the axis of symmetry.
  4. Connect the points with a parabola.

Finding the Axis of Symmetry

The axis of symmetry is a vertical line with equation Since we already know the values of and we can substitute them into the formula.
Simplify right-hand side
The axis of symmetry of the parabola is the vertical line with equation

Calculating the Vertex

To calculate the vertex, we need to think of as a function of We can write the expression for the vertex by stating the and coordinates in terms of and Note that the formula for the coordinate is the same as the formula for the axis of symmetry, which is Thus, the coordinate of the vertex is also To find the coordinate, we need to substitute for in the given equation.
Simplify right-hand side
We found the coordinate, and now we know that the vertex is

Identifying the intercept and its Reflection

The intercept of the graph of a quadratic function written in standard form is given by the value of Thus, the point where our graph intercepts the axis is Let's plot this point and its reflection across the axis of symmetry.

Connecting the Points

We can now draw the graph of the function. Since which is positive, the parabola will open upwards. Let's connect the three points with a smooth curve.

By looking at the graph, we can state approximated values for the intercepts. We can see that the parabola intercepts the axis at and approximately.