- Let f(x)= -6x + 3 and g(x) = 5x + 4. Find f•g and state its domain.

A: -30x^2 - 9x + 12; all real numbers except x = 4

B: -30x^2 - 9x + 12; all real numbers

C: -18x^2 - 39x + 20; all real numbers

D: -18x^2 - 39x + 20; all real numbers except x = 1

Respuesta :

Answer:

The function is [tex]\left(f \circ g \right) \left( x \right) = - 30 x - 21[/tex] and the domain is all real numbers.

Step-by-step explanation:

Composition of functions is when one function is inside of another function.

The notation used for the composition of functions looks like this, [tex]\left(f \circ g \right) \left( x \right) = f(g(x))[/tex].

We have the following functions

[tex]f(x)= -6x + 3\\\\g(x) = 5x + 4[/tex]

The composite function is

[tex]\left(f \circ g \right) \left( x \right) = f \left( g \left( x \right) \right)=f \left(5 x + 4 \right) = 3 - 6 {\left(5 x + 4\right)} = - 30 x - 21[/tex].

The domain is the set of all possible x-values which will make the function "work", and will output real y-values.

The function [tex]\left(f \circ g \right) \left( x \right) = - 30 x - 21[/tex] has no undefined points nor domain constraints. Therefore, the domain is [tex]-\infty \:<x<\infty \:[/tex] or all real numbers.

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