Which of the following describes the zeroes of the graph of [tex]f(x)=3 x^6+30 x^5+75 x^4[/tex]?

A. -5 with multiplicity 2 and [tex]\frac{1}{3}[/tex] with multiplicity 4
B. 5 with multiplicity 2 and [tex]\frac{1}{3}[/tex] with multiplicity 4
C. -5 with multiplicity 2 and 0 with multiplicity 4
D. 5 with multiplicity 2 and 0 with multiplicity 4



Answer :

To determine the zeros and their multiplicities for the function [tex]\(f(x) = 3x^6 + 30x^5 + 75x^4\)[/tex], let's follow these steps:

1. Find the Zeros of the Polynomial:
- First, factor the polynomial where possible.

[tex]\[ f(x) = 3x^6 + 30x^5 + 75x^4 \][/tex]

- Factor out the greatest common factor (GCF) from all terms:

[tex]\[ f(x) = 3x^4(x^2 + 10x + 25) \][/tex]

- Now, we need to factor the quadratic part, [tex]\( x^2 + 10x + 25 \)[/tex]:

[tex]\[ x^2 + 10x + 25 = (x + 5)^2 \][/tex]

- Substitute this back into our function:

[tex]\[ f(x) = 3x^4(x + 5)^2 \][/tex]

2. Identify the Zeros and Their Multiplicities:
- A zero occurs when [tex]\( f(x) = 0 \)[/tex].

[tex]\[ 3x^4(x + 5)^2 = 0 \][/tex]

- This equation is satisfied if any of the factors are zero:

[tex]\[ x^4 = 0 \quad \text{or} \quad (x + 5)^2 = 0 \][/tex]

- Solve for [tex]\( x \)[/tex]:

[tex]\[ x^4 = 0 \quad \Rightarrow \quad x = 0 \quad (\text{multiplicity 4}) \][/tex]

- From [tex]\((x + 5)^2 = 0\)[/tex]:

[tex]\[ (x + 5)^2 = 0 \quad \Rightarrow \quad x + 5 = 0 \quad \Rightarrow \quad x = -5 \quad (\text{multiplicity 2}) \][/tex]

3. Conclusion:
- The zeros of the polynomial [tex]\( f(x) = 3x^6 + 30x^5 + 75x^4 \)[/tex] are at [tex]\( x = 0 \)[/tex] with multiplicity 4 and [tex]\( x = -5 \)[/tex] with multiplicity 2.

Therefore, the correct description of the zeros is:

- [tex]\(-5\)[/tex] with multiplicity 2
- [tex]\(0\)[/tex] with multiplicity 4

Hence, the correct answer is:

- [tex]\(-5\)[/tex] with multiplicity 2 and [tex]\(0\)[/tex] with multiplicity 4