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Cory writes the polynomial [tex]\(x^7 + 3x^5 + 3x + 1\)[/tex]. Melissa writes the polynomial [tex]\(x^7 + 5x + 10\)[/tex].

Is there a difference between the degree of the sum and the degree of the difference of the polynomials?

A. Adding their polynomials together or subtracting one polynomial from the other both result in a polynomial with degree 7.
B. Adding their polynomials together or subtracting one polynomial from the other both result in a polynomial with degree 5.
C. Adding their polynomials together results in a polynomial with degree 14, but subtracting one polynomial from the other results in a polynomial with degree 5.
D. Adding their polynomials together results in a polynomial with degree 7, but subtracting one polynomial from the other results in a polynomial with degree 5.


Sagot :

Alright, let's look at the polynomials given:

Cory's polynomial: [tex]\( P(x) = x^7 + 3x^5 + x \)[/tex]
Melissa's polynomial: [tex]\( Q(x) = x^7 + 5x + 10 \)[/tex]

### Step-by-Step Solution

1. Adding the polynomials:

When we add the polynomials [tex]\( P(x) \)[/tex] and [tex]\( Q(x) \)[/tex]:
[tex]\[ P(x) + Q(x) = (x^7 + 3x^5 + x) + (x^7 + 5x + 10) \][/tex]
Combine like terms:
[tex]\[ (x^7 + x^7) + 3x^5 + (x + 5x) + 10 \][/tex]
[tex]\[ = 2x^7 + 3x^5 + 6x + 10 \][/tex]

The degree of the resulting polynomial is determined by the highest power of [tex]\( x \)[/tex], which is:

[tex]\[ \text{Degree of } (P(x) + Q(x)) = 7 \][/tex]

2. Subtracting the polynomials:

When we subtract polynomial [tex]\( Q(x) \)[/tex] from [tex]\( P(x) \)[/tex]:
[tex]\[ P(x) - Q(x) = (x^7 + 3x^5 + x) - (x^7 + 5x + 10) \][/tex]
Combine like terms:
[tex]\[ (x^7 - x^7) + 3x^5 + (x - 5x) - 10 \][/tex]
[tex]\[ = 0 + 3x^5 - 4x - 10 \][/tex]
[tex]\[ = 3x^5 - 4x - 10 \][/tex]

The degree of the resulting polynomial is determined by the highest power of [tex]\( x \)[/tex], which is:

[tex]\[ \text{Degree of } (P(x) - Q(x)) = 5 \][/tex]

3. Conclusion:

By comparing the degrees:
- The degree of the polynomial after addition is [tex]\(7\)[/tex].
- The degree of the polynomial after subtraction is [tex]\(5\)[/tex].

Hence, adding their polynomials together results in a polynomial with degree 7, but subtracting one polynomial from the other results in a polynomial with degree 5. Therefore, there is a difference between the degree of the sum and the degree of the difference of the polynomials.

The correct option is:
- Adding their polynomials together results in a polynomial with degree 7, but subtracting one polynomial from the other results in a polynomial with degree 5.