Difference between revisions of "1980 AHSME Problems/Problem 2"

(Solution 2)
(Solution 1)
 
Line 7: Line 7:
 
== Solution 1==
 
== Solution 1==
  
Expanding each factor yields <math>(x^{8}+...)(x^{9}+...)</math>. The degree of the first factor is <math>8</math>, while the degree of the second factor is <math>9</math>. Therefore, the degree of the polynomial is <math>8 + 9 = \boxed{17\  (\textbf{D})}</math>
+
Expanding each factor yields <math>(x^{8}+...)(x^{9}+...)</math>. The degree of the first factor is <math>8</math>, while the degree of the second factor is <math>9</math>. Therefore, the degree of the polynomial is <math>8 + 9 = \boxed{(\textbf{D})\ 17}</math>
  
 
==Solution 2==
 
==Solution 2==

Latest revision as of 01:14, 14 July 2025

Problem

The degree of $(x^2+1)^4 (x^3+1)^3$ as a polynomial in $x$ is

$\text{(A)} \ 5 \qquad \text{(B)} \ 7 \qquad \text{(C)} \ 12 \qquad \text{(D)} \ 17 \qquad \text{(E)} \ 72$

Solution 1

Expanding each factor yields $(x^{8}+...)(x^{9}+...)$. The degree of the first factor is $8$, while the degree of the second factor is $9$. Therefore, the degree of the polynomial is $8 + 9 = \boxed{(\textbf{D})\ 17}$

Solution 2

Let $\deg{P(x)}$ be the degree of a polynomial in $x$. Recall that for any polynomials $P(x)$ and $Q(x)$, and nonnegative integer $n$, $\deg{(P(x)^n)} = n \deg{P(x)}$ and $\deg{(P(x)Q(x))} = \deg {P(x)} + \deg {Q(x)}$.

So $\deg{((x^2+1)^4(x^3+1)^3)}$ $= \deg{((x^2+1)^4)} + \deg{((x^3+1)^3)}$ $= 4 \deg{(x^2+1)} + 3 \deg{(x^3+1)}$ $= 4 \cdot 2 + 3 \cdot 3$ $= \boxed{(\textbf{D})\ 17}$.

-mihirb, edited by j314andrews

See also

1980 AHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 1
Followed by
Problem 3
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
All AHSME Problems and Solutions

These problems are copyrighted © by the Mathematical Association of America, as part of the American Mathematics Competitions. AMC Logo.png