# Write an equation for a parabola given vertex and y intercept

Features of quadratic functions Video transcript We need to find the vertex and the axis of symmetry of this graph. The whole point of doing this problem is so that you understand what the vertex and axis of symmetry is. I would like to know how to find the equation of a quadratic function from its graph, including when it does not cut the x-axis.

## Graphing Parabolas in Vertex Form

Modelling This is a good question because it goes to the heart of a lot of "real" math. Most "text book" math is the wrong way round - it gives you the function first and asks you to plug values into that function.

The parabola can either be in "legs up" or "legs down" orientation. We know that a quadratic equation will be in the form: Sometimes it is easy to spot the points where the curve passes through, but often we need to estimate the points.

Parabola cuts the graph in 2 places We can see on the graph that the roots of the quadratic are: But is this the correct answer?

Here are some of them in green: So how do we find the correct quadratic function for our original question the one in blue?

System of Equations method To find the unique quadratic function for our blue parabola, we need to use 3 points on the curve. We can then form 3 equations in 3 unknowns and solve them to get the required result. Vertex method Another way of going about this is to observe the vertex the "pointy end" of the parabola.

We can write a parabola in "vertex form" as follows: If there are no other "nice" points where we can see the graph passing through, then we would have to use our estimate. The next example shows how we can use the Vertex Method to find our quadratic function.

One point touching the x-axis This parabola touches the x-axis at 1, 0 only. What is the value of "a"? But as in the previous case, we have an infinite number of parabolas passing through 1, 0. Here are some of them: We can see the vertex is at -2, 1 and the y-intercept is at 0, 2.

We just substitute as before into the vertex form of our quadratic function.Given a quadratic equation of the form y = a x 2 + b x + c, x is the independent variable and y is the dependent variable. Choose some values for x and then determine the corresponding y -values.

## Write the equation of each parabola? | Yahoo Answers

Then plot the points and sketch the graph. Name: _____ Date _____ Tons of Free Math Worksheets at: © initiativeblog.com Jul 22,  · Given the example equation y = x^2 - 2x - 15, analyze the parabola it represents into the above elements: Find that the element a is missing and must therefore equal 1, which is positive, so the graph has a minimum and opens initiativeblog.com: K.

Mar 28,  · Write an equation in vertex form of the parabola that has the same shape as the graph of f(x) = 2x2, but with the point (7, 4) as its initiativeblog.com: Resolved.

Improve your math knowledge with free questions in "Write equations of parabolas in vertex form from graphs" and thousands of other math skills. IXL Learning Learning.

 initiativeblog.com | Writing Quadratic Equations Given Three Points on a Parabola For other uses, see Parabola disambiguation. How to Find the Vertex of a Quadratic Equation: 10 Steps How to use the parabola equation calculator: Definition Due to the nature of the mathematics on this site it is best views in landscape mode. Vertex and x-y intercept of quadratic? - initiativeblog.com Focus and directrix of a parabola conic sections Video transcript - [Voiceover] What I have attempted to draw here in yellow is a parabola, and as we've already seen in previous videos, a parabola can be defined as the set of all points that are equidistant to a point and a line, and the point is called the focus of the parabola, and the line is called the directrix of the parabola. To Find The Tangent Of Gradient M For other uses, see Parabola disambiguation.  