Connect with experts and get insightful answers to your questions on IDNLearn.com. Our platform is designed to provide reliable and thorough answers to all your questions, no matter the topic.

Which are cubic functions? Check all that apply.

A. [tex]f(x) = -4 - 2x + 5x^3[/tex]

B. [tex]f(x) = -3^x - 1[/tex]

C. [tex]f(x) = -x^2 + 5x - x^3[/tex]

D. [tex]f(x) = x^2 - 6x^3 + 2x^4 + 1[/tex]

E. [tex]f(x) = 2x^3 + 3x^2 - x - 3[/tex]

F. [tex]f(x) = 3x^2 - 1 - 8x[/tex]


Sagot :

To determine which of the given functions are cubic functions, we need to recall that a cubic function is a polynomial of degree 3. This means it is of the form [tex]\( ax^3 + bx^2 + cx + d \)[/tex], where [tex]\( a \)[/tex], [tex]\( b \)[/tex], [tex]\( c \)[/tex], and [tex]\( d \)[/tex] are constants, and the highest power of [tex]\( x \)[/tex] is [tex]\( 3 \)[/tex].

Let’s analyze each function step by step:

1. [tex]\( f(x) = -4 - 2x + 5x^3 \)[/tex]
- The highest power of [tex]\( x \)[/tex] is [tex]\( x^3 \)[/tex], and there are no higher powers of [tex]\( x \)[/tex].
- Therefore, this function is a cubic function.

2. [tex]\( f(x) = -3^x - 1 \)[/tex]
- The term [tex]\( 3^x \)[/tex] is an exponential term, not a polynomial term, as the variable [tex]\( x \)[/tex] is in the exponent.
- Since it is not a polynomial, it cannot be a cubic function.

3. [tex]\( f(x) = -x^2 + 5x - x^3 \)[/tex]
- The highest power of [tex]\( x \)[/tex] is [tex]\( x^3 \)[/tex], and there are no higher powers of [tex]\( x \)[/tex].
- Therefore, this function is a cubic function.

4. [tex]\( f(x) = x^2 - 6x^3 + 2x^4 + 1 \)[/tex]
- The highest power of [tex]\( x \)[/tex] is [tex]\( x^4 \)[/tex].
- Since the highest power of [tex]\( x \)[/tex] is [tex]\( 4 \)[/tex], this function is a quartic function, not a cubic function.

5. [tex]\( f(x) = 2x^3 + 3x^2 - x - 3 \)[/tex]
- The highest power of [tex]\( x \)[/tex] is [tex]\( x^3 \)[/tex], and there are no higher powers of [tex]\( x \)[/tex].
- Therefore, this function is a cubic function.

6. [tex]\( f(x) = 3x^2 - 1 - 8x \)[/tex]
- The highest power of [tex]\( x \)[/tex] is [tex]\( x^2 \)[/tex].
- Since the highest power of [tex]\( x \)[/tex] is [tex]\( 2 \)[/tex], this function is a quadratic function, not a cubic function.

From this analysis, the cubic functions among the given options are:
[tex]\[ f(x) = -4 - 2x + 5x^3 \][/tex]
[tex]\[ f(x) = -x^2 + 5x - x^3 \][/tex]
[tex]\[ f(x) = 2x^3 + 3x^2 - x - 3 \][/tex]

Therefore, the cubic functions are:
[tex]\[ f(x) = -4 - 2x + 5x^3 \][/tex]
[tex]\[ f(x) = -x^2 + 5x - x^3 \][/tex]
[tex]\[ f(x) = 2x^3 + 3x^2 - x - 3 \][/tex]