If [tex]s(x) = x - 7[/tex] and [tex]t(x) = 4x^2 - x + 3[/tex], which expression is equivalent to [tex](t \circ s)(x)[/tex]?

A. [tex]4(x-7)^2 - x - 7 + 3[/tex]
B. [tex]4(x-7)^2 - (x-7) + 3[/tex]
C. [tex](4x^2 - x + 3) - 7[/tex]
D. [tex](4x^2 - x + 3)(x-7)[/tex]



Answer :

In this problem, we want to find the expression that represents [tex]\((t \circ s)(x)\)[/tex], where the function [tex]\(s(x) = x - 7\)[/tex] and the function [tex]\(t(x) = 4x^2 - x + 3\)[/tex].

The composition [tex]\((t \circ s)(x)\)[/tex] means we first apply the function [tex]\(s(x)\)[/tex] and then apply the function [tex]\(t(x)\)[/tex] on the result of [tex]\(s(x)\)[/tex].

1. Apply [tex]\(s(x)\)[/tex]:
[tex]\[ s(x) = x - 7 \][/tex]

2. Apply [tex]\(t\)[/tex] on [tex]\(s(x)\)[/tex]:
[tex]\[ t(s(x)) = t(x - 7) \][/tex]

3. Evaluate [tex]\(t(x - 7)\)[/tex] by substituting [tex]\(x - 7\)[/tex] into the function [tex]\(t(x)\)[/tex]:

Since [tex]\(t(x) = 4x^2 - x + 3\)[/tex], we substitute [tex]\(x - 7\)[/tex] into [tex]\(t(x)\)[/tex]:

[tex]\[ t(x - 7) = 4(x - 7)^2 - (x - 7) + 3 \][/tex]

This is the expanded form. Let's simplify it step-by-step:

4. Square the binomial [tex]\((x - 7)\)[/tex]:
[tex]\[ (x - 7)^2 = x^2 - 14x + 49 \][/tex]

5. Substitute this back into the expression:

[tex]\[ t(x - 7) = 4(x^2 - 14x + 49) - (x - 7) + 3 \][/tex]

6. Distribute the 4:
[tex]\[ 4(x^2 - 14x + 49) = 4x^2 - 56x + 196 \][/tex]

7. Combine all terms:
[tex]\[ t(x - 7) = 4x^2 - 56x + 196 - (x - 7) + 3 \][/tex]

Simplify the terms inside the expression:

[tex]\[ t(x - 7) = 4x^2 - 56x + 196 - x + 7 + 3 \][/tex]

Combine like terms:

[tex]\[ t(x - 7) = 4x^2 - 57x + 206 \][/tex]

None of the choices simplified to this. However, there seems to be a typo in the choices given; correct one among presented option is:

[tex]\[ t(x - 7) = 4(x - 7)^2 - (x - 7) + 3 \][/tex]

Thus, the correct simplified form given is:

[tex]\[ t(x - 7) = \boxed{4(x-7)^2-(x-7)+3} \][/tex]

Notice that (x - 7)^2 can simplify further hence the final form is:
This matches one of the provided options precisely.

[tex]\[ \boxed{4(x - 7)^2 - (x - 7) + 3} \][/tex]

Thus, the correct answer is:
[tex]\[ \boxed{4(x - 7)^2 - (x - 7) + 3} \][/tex]