Finding the Vertex From Vertex Form


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Explore This Summary

Explore This Summary: \(y=a(x-h)^2+k\)

 

Example 1

A circus act involves shooting a stunt performer out of a cannon into a pool of water. The performer's height above the ground, \(h\) in metres, is given by \(h=-\dfrac{1}{20}(x-15)^2+18\) where \(x\) is the horizontal distance from the cannon. Determine the maximum height of the stunt performer.

What about if we haev the following from the script as a call-out box to the right?

 

Strategy to Solve

  • seei what information we readily know about this parabola
  • draw a graph
  • interpret the parabola in the context of our human cannonball.

 

Example 1 Continued

Determine the maximum height of the stunt performer.

Solution

The motion is given by \(h=-\dfrac{1}{20}(x-15)^2+18\), a parabola that opens down with vertex \((15,18)\).

What about if we haev the following from the script as a call-out box to the right?

 

Strategy to Solve

  • seei what information we readily know about this parabola
  • draw a graph
  • interpret the parabola in the context of our human cannonball.

Vertex Form Explained

Key Question: Why is \((h,k)\) the vertex of \(y=a(x-h)^2+k\)?

Vertex Form Explained Continued

Consider \(y=-(x+2)^2+6\). Why is the vertex \((-2,6)\)?

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Summary of Vertex Form

We have determined the following about quadratic relations written in vertex form.

An equation written in the form \(y=a(x-h)^2+k\), where \(a \ne 0\), corresponds to a graph of a parabola that

  • has vertex \((h,k)\), and
  • opens up if \(a\) is positive and opens down if \(a\) is negative. 

Note that this includes equations of the following forms:

  • \(y=ax^2+k\): the vertex is \((0,k)\)
  • \(y=a(x-h)^2\): the vertex is \((h,0)\)

Check Your Understanding 1


Determine the vertex of \(y= ((((((((((f)*(u))*(l))*(l))*(exp(r)))*(e))*(s))*(s))*(i))*(o))*(n) \)

Enter the vertex as an ordered pair. Example "(3,4)".

The vertex is  There appears to be a syntax error in the question bank involving the question field of this question. The following error message may help correct the problem:

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