Which statement describes the inverse of [tex]m(x)=x^2-17x[/tex]?

A. The domain restriction [tex]x \geq \frac{17}{2}[/tex] results in [tex]m^{-1}(x) = \frac{17}{2} - \sqrt{x + \frac{289}{4}}[/tex]
B. The domain restriction [tex]x \geq \frac{17}{2}[/tex] results in [tex]m^{-1}(x) = \frac{17}{2} + \sqrt{x + \frac{289}{4}}[/tex]
C. The domain restriction [tex]x \geq -\frac{17}{2}[/tex] results in [tex]m^{-1}(x) = \frac{17}{2} - \sqrt{x + \frac{289}{4}}[/tex]
D. The domain restriction [tex]x \geq -\frac{17}{2}[/tex] results in [tex]m^{-1}(x) = \frac{17}{2} + \sqrt{x + \frac{289}{4}}[/tex]



Answer :

To find the inverse of the function [tex]\( m(x) = x^2 - 17x \)[/tex], we want to solve for [tex]\( x \)[/tex] in terms of [tex]\( y \)[/tex], where [tex]\( y = m(x) \)[/tex].

1. Start by setting [tex]\( y = x^2 - 17x \)[/tex].

[tex]\[ y = x^2 - 17x \][/tex]

2. Rearrange the equation to solve for [tex]\( x \)[/tex].

[tex]\[ x^2 - 17x - y = 0 \][/tex]

This is a quadratic equation in standard form [tex]\( ax^2 + bx + c = 0 \)[/tex], where [tex]\( a = 1 \)[/tex], [tex]\( b = -17 \)[/tex], and [tex]\( c = -y \)[/tex].

3. Solve the quadratic equation using the quadratic formula:

[tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]

Plug in the values of [tex]\( a \)[/tex], [tex]\( b \)[/tex], and [tex]\( c \)[/tex]:

[tex]\[ x = \frac{17 \pm \sqrt{17^2 - 4 \cdot 1 \cdot (-y)}}{2 \cdot 1} \][/tex]

[tex]\[ x = \frac{17 \pm \sqrt{289 + 4y}}{2} \][/tex]

[tex]\[ x = \frac{17 \pm \sqrt{4y + 289}}{2} \][/tex]

Therefore, we have two solutions:

[tex]\[ x_1 = \frac{17 + \sqrt{4y + 289}}{2} \][/tex]

[tex]\[ x_2 = \frac{17 - \sqrt{4y + 289}}{2} \][/tex]

4. To determine which expression to use for the inverse function [tex]\( m^{-1}(x) \)[/tex], we need to consider the domain restriction. Given the domain restriction [tex]\( x \geq \frac{17}{2} \)[/tex]:

[tex]\[ \frac{17}{2} = 8.5 \][/tex]

5. Substitute [tex]\( x = 8.5 \)[/tex] into both solutions to check which one satisfies the domain restriction:

[tex]\[ x_1 = \frac{17 + \sqrt{4y + 289}}{2} = 17 - \frac{\sqrt{4y + 289}}{2} \][/tex]

Given the restriction [tex]\( x \geq 8.5 \)[/tex]:

[tex]\[ \frac{17 - \sqrt{4y + 289}}{2} \leq 8.5 \][/tex]

Since [tex]\( 17 - \sqrt{4y + 289} \geq 8.5 \)[/tex], the feasible solution satisfying the domain restriction is:

[tex]\[ x_2 = \frac{17 + \sqrt{4y + 289}}{2} \][/tex]

6. Therefore, considering the inverse function [tex]\( m^{-1}(x) \)[/tex] with the given domain restriction:

[tex]\[ m^{-1}(x) = \frac{17 - \sqrt{4y + 289}}{2} \][/tex]

Thus, the correct statement is:

The domain restriction [tex]\( x \geq \frac{17}{2} \)[/tex] results in [tex]\( m^{-1}(x) = \frac{17 - \sqrt{x + \frac{289}{4}}} \)[/tex].