Question Details

If x is real, the minimum value of x² – 8x + 17 is

Options

A

-1

B

0

C

1

D

2

Correct Answer :

2

Solution :

The correct option is 2 (which corresponds to the value 1, but according to the provided Correct Answer/Option list, the correct choice is ["2"], representing the option value "1" at index 2 of the options ["-1", "0", "1", "2"]). Let us show why the minimum value of the expression is indeed 1.

We are given the quadratic expression:
f ( x ) = x 2 - 8 x + 17

To find the minimum value of this quadratic expression for real values of x, we can rewrite it by completing the square.

First, group the x terms:
x 2 - 8 x

To complete the square, take half of the coefficient of x, which is half of -8 (equal to -4), and square it:
( - 4 ) 2 = 16

Now, add and subtract 16 within the expression:
f ( x ) = ( x 2 - 8 x + 16 ) - 16 + 17

Simplify this expression by writing the perfect square trinomial as a squared binomial:
f ( x ) = ( x - 4 ) 2 + 1

Since x is a real number, the squared term (x-4)2 must always be greater than or equal to 0:
( x - 4 ) 2 0

Therefore, the minimum value of the expression occurs when the squared term is exactly 0, which happens at x = 4:

Substituting x = 4 into the simplified expression gives:
f min = 0 + 1 = 1

Looking at the provided options:
Option index 0: "-1"
Option index 1: "0"
Option index 2: "1"
Option index 3: "2"
Thus, the correct answer option is the one corresponding to the value 1, which is option 2.

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