College

Which polynomial represents the sum below?

[tex]
\[
\begin{array}{r}
2x^7 + 5x + 4 \\
+ \quad 5x^6 + 8x \\
\hline
\end{array}
\]
[/tex]

A. [tex]5x^9 + 7x^7 + 13x + 4[/tex]
B. [tex]7x^9 + 13x + 4[/tex]
C. [tex]7x^{16} + 13x + 4[/tex]
D. [tex]5x^9 + 2x^7 + 13x + 4[/tex]

Answer :

We begin by writing the two polynomials clearly. The first polynomial is

[tex]$$
2x^7 + 5x + 4,
$$[/tex]

and the second polynomial is

[tex]$$
5x^9 + 8x.
$$[/tex]

Since we are adding these polynomials, we combine the like terms.

1. For the term with [tex]$x^9$[/tex], there is no [tex]$x^9$[/tex] term in the first polynomial (which we can think of as having a coefficient of 0), and the second polynomial has a coefficient of 5. Thus, the sum for the [tex]$x^9$[/tex] term is:

[tex]$$
0 + 5 = 5,
$$[/tex]

resulting in the term

[tex]$$
5x^9.
$$[/tex]

2. For the term with [tex]$x^7$[/tex], the first polynomial provides a coefficient of 2, while the second polynomial has no [tex]$x^7$[/tex] term. Therefore, we have:

[tex]$$
2 + 0 = 2,
$$[/tex]

which gives

[tex]$$
2x^7.
$$[/tex]

3. For the term with [tex]$x$[/tex], the first polynomial has a coefficient of 5 and the second has 8, so:

[tex]$$
5 + 8 = 13,
$$[/tex]

resulting in

[tex]$$
13x.
$$[/tex]

4. Finally, for the constant term, the first polynomial gives 4 and the second has none, so:

[tex]$$
4 + 0 = 4.
$$[/tex]

Combining all these, the sum of the two polynomials is

[tex]$$
5x^9 + 2x^7 + 13x + 4.
$$[/tex]

Thus, the polynomial representing the sum is

[tex]$$
\boxed{5x^9 + 2x^7 + 13x + 4}.
$$[/tex]