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For what value of x does the function f(x) = 4x2 - 2x + 8 assume its minimum value?

 May 28, 2015

Best Answer 

 #1
avatar+128732 
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f(x) = 4x^2 - 2x + 8    .....taking the derivative and setting it to 0, we have

 

f ' (x)  = 8x - 2  = 0

 

8x = 2

 

x = 1/4

 

f(1/4) = 4(1/4)^2 - 2(1/4) + 8  =  1/4 - 1/2 + 8 =  7.75

 

So....the minimum occurs at  (1/4 , 7.75)  = (.25, 7.75)        .....and since this parabola turns "upward," we can be sure this is the miinimum

 

 

 May 28, 2015
 #1
avatar+128732 
+5
Best Answer

f(x) = 4x^2 - 2x + 8    .....taking the derivative and setting it to 0, we have

 

f ' (x)  = 8x - 2  = 0

 

8x = 2

 

x = 1/4

 

f(1/4) = 4(1/4)^2 - 2(1/4) + 8  =  1/4 - 1/2 + 8 =  7.75

 

So....the minimum occurs at  (1/4 , 7.75)  = (.25, 7.75)        .....and since this parabola turns "upward," we can be sure this is the miinimum

 

 

CPhill May 28, 2015

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