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What is the standard form of the quadratic function that has a vertex at (3,-2) and goes through the point (4,0)?

 Apr 8, 2020
 #1
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What is the standard form of the quadratic function that has a vertex at (3,-2) and goes through the point (4,0)?

 

Here is the easy way:

the axis of symmetry is x=3 with vertex at y=-2

one root is at 4   

3+1=4

3-1=2

so the other root is at 2

y=k(x2)(x4)subin(3,2)2=k11k=2y=2(x2)(x4)y=2(x26x+8)y=2x212x+16

 

 

Or if you prefer the harder way.  then...

 

(xh)2=4a(yk)(x3)2=4a(y+2)subin(4,0)(43)2=4a(0+2)1=8aa=0.125 (x3)2=40.125(y+2)x26x+9=0.5y+1x26x+8=0.5yy=2x212x+16

 

 

 

 

Coding:

 

y=k(x-2)(x-4)\\
sub\;in\; (3,-2)\\
-2=k*1*-1\\
k=2\\
y=2(x-2)(x-4)\\
y=2(x^2-6x+8)\\
y=2x^2-12x+16

 

 

(x-h)^2=4a(y-k)\\
(x-3)^2=4a(y+2)\\
sub\;\; in\;\; (4,0)\\
(4-3)^2=4a(0+2)\\
1=8a\\
a=0.125\\~\\
(x-3)^2=4*0.125(y+2)\\

x^2-6x+9=0.5y+1\\

x^2-6x+8=0.5y\\

y=2x^2-12x+16

 Apr 8, 2020

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