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if f(1) = 5, f(2) = 8 and f(x) = ax+bx+2, what is the value of f(3)?

 Jan 30, 2019
 #1
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I think this might be :  f(x) = ax^2 + bx + c

 

if f(1) = 5, f(2) = 8 and f(x) = ax^2+bx+2, what is the value of f(3)

 

f(1)  =  a + b + 2  = 5    ⇒  2a + 2b + 4 = 10   (1) 

 

f(2) =  4a  + 2b + 2 = 8      (2)    subtract (1) from (2)  and we have that

 

 

2a - 2 = -2     add 2a to both sides

 

2a = 0

 

a = 0

 

And we can find b as

 

2(0)  + 2b + 4 = 10

2b =  6

b = 3

 

So....the function is just

 

f(x) =   3b + 2

 

f(3) = 3(3) + 2  =   11

 

 

cool cool cool

 Jan 30, 2019

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