Question Details

Find the interval in which function f(x) = x2 – 4x + 5 is increasing

Options

A

(-∞, 2)

B

(2, ∞)

C

(-∞, ∞)

D

(3, ∞)

Correct Answer :

(2, ∞)

Solution :

The correct option is (2, ∞).

To find the interval in which the quadratic function
f ( x ) = x 2 4 x + 5
is increasing, we need to determine where its first derivative is strictly positive, i.e., f(x)>0.

Step 1: Find the derivative of the function
We apply the power rule of differentiation to each term of the function:
f ( x ) = d d x ( x 2 4 x + 5 )
f ( x ) = 2 x 4

Step 2: Set up the inequality for an increasing function
A function is increasing on an interval where its derivative is positive:
f ( x ) > 0
Substituting the derivative we found:
2 x 4 > 0

Step 3: Solve the inequality for x
Add 4 to both sides of the inequality:
2 x > 4
Divide both sides by 2:
x > 2

Conclusion:
Since x>2, the function is increasing on the interval from 2 to infinity, which is represented in interval notation as (2, ∞).

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