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Use the inverse of the function [tex][tex]$y=x^2-18x$[/tex][/tex] to find the unknown values.

[tex]\[
\begin{array}{l}
b = \square \\
y = \pm \sqrt{bx+c} + d \\
c = \square \\
d = \square
\end{array}
\][/tex]

Sagot :

Sure, let's find the values of [tex]\( b \)[/tex], [tex]\( c \)[/tex], and [tex]\( d \)[/tex] in the inverse function of [tex]\( y = x^2 - 18x \)[/tex].

1. Original Function:
[tex]\[ y = x^2 - 18x \][/tex]

2. To find the inverse function, we swap [tex]\( x \)[/tex] and [tex]\( y \)[/tex], so:
[tex]\[ x = y^2 - 18y \][/tex]

3. This is a standard quadratic equation in [tex]\( y \)[/tex]:
[tex]\[ y^2 - 18y - x = 0 \][/tex]

4. We solve this quadratic equation using the quadratic formula: [tex]\( y = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \)[/tex] where [tex]\( a = 1 \)[/tex], [tex]\( b = -18 \)[/tex], and [tex]\( c = -x \)[/tex]. Therefore:
[tex]\[ y = \frac{18 \pm \sqrt{324 + 4x}}{2} \][/tex]

5. The inverse function, represented in the form [tex]\( y = \pm \sqrt{bx + c} + d \)[/tex], corresponds to comparing the above solution to this form. We compare:
[tex]\[ y = \frac{18 \pm \sqrt{324 + 4x}}{2} \quad \text{with} \quad y = \pm \sqrt{bx + c} + d \][/tex]

6. Upon comparing, it fits [tex]\( y = \pm \sqrt{4x + 324} + 9 \)[/tex]. Therefore:
[tex]\[ \pm \sqrt{bx + c} + d = \pm \sqrt{4x + 324} + 9 \][/tex]

7. Thus, the values of [tex]\( b \)[/tex], [tex]\( c \)[/tex], and [tex]\( d \)[/tex] are:
[tex]\[ b = 4, \quad c = 324, \quad d = 9 \][/tex]

So the unknown values are:
[tex]\[ \begin{array}{l} b = 4 \\ c = 324 \\ d = 9 \end{array} \][/tex]