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A parabola with equation y=x^2+bx+c passes through the points (2,3) and (4,3). What is c?

 Oct 9, 2019
 #1
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We have these two equations

 

3  = (2)^2 + 2b + c

3 =  (4)^2 + 4b + c   simplify

 

3 = 4 + 2b + c

3  = 16 + 4b + c

 

-1  = 2b + c    ⇒   2 = -4b  - 2c    (1)

-13 = 4b + c      (2)

 

Add (1) and (2)  and we have

 

-11 = -c

 

c  = 11

 

 

cool cool cool

 Oct 9, 2019

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