Question 1148201: How do i make a quadratic equation from vertex point (4,-3) and point (6,-1)? Found 3 solutions by josmiceli, MathTherapy, greenestamps:Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website! The general form is
The y-component of ( 6, -1 ) is greater than the
y-component of the vertex, so I know the vertex is
a minimum ( just an observation )
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( 4, -3 )
(1)
------------------------------
For the vertex:
(2)
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( 6, -1 )
(3)
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You have 3 equation with 3 unknowns, so
it's solvable
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Plug (2) into (1) and (3)
(1)
(1)
(1)
--------------------------------
(3)
(3)
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Subtract (1) from (3)
(3)
(1)
------------------------------
and
(2)
(2)
and
(3)
(3)
(3)
(3)
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The equation is:
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check:
( 4, -3 )
OK
and
( 6, -1 )
OK
Here's the plot:
Looks OK
Vertex form of a quadratic: ------- Substituting (4, - 3) for (h, k), and (6, - 1) for (x, y)
- 1 = 4a - 3
- 1 + 3 = 4a
2 = 4a ----- Substituting for a, and (4, - 3) for (h, k)
That's it!! Nothing complex or time-consuming, @ ALL!
Start with the vertex form of the equation, as tutor @MathTherapy did:
With the vertex given as (4,-3), the equation in this form is
Then here is an alternative method for determining the value of a to complete the equation.
(1) The point other than the vertex that is given is 2 units to the right of the vertex.
(2) If a were 1, so that the graph behaved like y=x^2, then the y value 2 to the right of the vertex would be 2^2=4 greater than the y value at the vertex.
(3) But the y value 2 to the right of the vertex is only 2 greater than the y value at the vertex.
Since the y value increased only half as much as it would have increased if a were 1, a must be 1/2.