If [tex]f(x) = 4 - x^2[/tex] and [tex]g(x) = 6x[/tex], which expression is equivalent to [tex](g - f)(3)[/tex]?

A. [tex]6 - 3 - (4 + 3)^2[/tex]
B. [tex]6 - 3 - \left(4 - 3^2\right)[/tex]
C. [tex]6(3) - 4 + 3^2[/tex]
D. [tex]6(3) - 4 - 3^2[/tex]



Answer :

To find which expression is equivalent to [tex]\((g - f)(3)\)[/tex] where [tex]\(f(x) = 4 - x^2\)[/tex] and [tex]\(g(x) = 6x\)[/tex], let's go through the following steps:

1. Calculate [tex]\(g(3)\)[/tex]:
[tex]\[ g(3) = 6 \cdot 3 = 18 \][/tex]

2. Calculate [tex]\(f(3)\)[/tex]:
[tex]\[ f(3) = 4 - 3^2 = 4 - 9 = -5 \][/tex]

3. Find [tex]\((g - f)(3)\)[/tex]:
[tex]\[ (g - f)(3) = g(3) - f(3) \][/tex]
Substituting the values we found:
[tex]\[ (g - f)(3) = 18 - (-5) = 18 + 5 = 23 \][/tex]

Now we need to compare the given expressions to find out which one matches 23 when evaluated.

- First option: [tex]\(6-3-(4+3)^2\)[/tex]
[tex]\[ 6 - 3 - (4 + 3)^2 = 6 - 3 - 7^2 = 6 - 3 - 49 = 3 - 49 = -46 \][/tex]
This does not match 23.

- Second option: [tex]\(6-3-\left(4-3^2\right)\)[/tex]
[tex]\[ 6 - 3 - (4 - 3^2) = 6 - 3 - (4 - 9) = 6 - 3 - (-5) = 6 - 3 + 5 = 3 + 5 = 8 \][/tex]
This does not match 23.

- Third option: [tex]\(6(3)-4+3^2\)[/tex]
[tex]\[ 6 \cdot 3 - 4 + 3^2 = 18 - 4 + 9 = 14 + 9 = 23 \][/tex]
This matches [tex]\(23\)[/tex].

- Fourth option: [tex]\(6(3)-4-3^2\)[/tex]
[tex]\[ 6 \cdot 3 - 4 - 3^2 = 18 - 4 - 9 = 18 - 13 = 5 \][/tex]
This does not match 23.

Therefore, the expression [tex]\(6(3)-4+3^2\)[/tex] correctly matches [tex]\((g - f)(3) = 23\)[/tex].