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find a formula for the quad. function whose graph has vertex @ (5,4) and its y-int at y=-4

 Mar 3, 2019
 #1
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We have that

 

y = a (x - 5)^2 + 4

 

And if the y intercept is - 4, then (0, -4) is on the graph, we have

 

- 4 = a(0 - 5)^2 + 4

 

- 4 = 25a + 4     subtract 4 from both sides

 

-8 = 25a      divide both sides by 25

 

a = -8/25

 

So......the function is

 

y = (-8/25) ( x - 5)^2 + 4     simplify

 

y = (-8/25) ( x ^2 - 10x + 25) + 4

 

y = (-8/25)x^2 + (16/5)x - 8 + 4

 

y = (-25/8)x^2 + (16/5)x - 4

 

 

cool cool cool

 Mar 4, 2019

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