Value of the 7th term in (2x + y)"?

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter10: Sequences, Series, And Probability
Section10.5: The Binomial Theorem
Problem 19E
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### Algebra 2B - GENET 21-22 (MI)

#### Module: Binomial Expansion

**Question 4:** What is the value of the 7th term in \((2x + y)^9\)?

**Options:**

a) \( \binom{9}{6} (2x)^{9-6} (y)^6 \)

b) \( \binom{9}{6} (a)^{9-6} (b)^6 \)

c) \( \binom{9}{6} (2x)^{9-6} (y)^6 \)

d) \( \binom{9}{6} (ax)^{9-6} (b)^{6-6} \)

**Explanation:**

To find the 7th term in the binomial expansion of \((2x + y)^9\), we can use the general term formula in the binomial theorem:

\[ T_{k+1} = \binom{n}{k} a^{n-k} b^k \]

Given that \( n = 9 \), \( a = 2x \), and \( b = y \):

For the 7th term (\( k = 6 \)), we calculate as follows:

\[ T_{6+1} = \binom{9}{6} (2x)^{9-6} (y)^6 \]

which simplifies to:

\[ \binom{9}{6} (2x)^3 y^6 \]

By comparing this with the given options, we find that the correct option is:

\[ \boxed{ \binom{9}{6} (2x)^{9-6} (y)^6 } \]

(\(Note: This is both option (a) and option (c).\))

For deeper understanding, students can refer to the binomial theorem and practice expanding binomials for a variety of expressions.
Transcribed Image Text:### Algebra 2B - GENET 21-22 (MI) #### Module: Binomial Expansion **Question 4:** What is the value of the 7th term in \((2x + y)^9\)? **Options:** a) \( \binom{9}{6} (2x)^{9-6} (y)^6 \) b) \( \binom{9}{6} (a)^{9-6} (b)^6 \) c) \( \binom{9}{6} (2x)^{9-6} (y)^6 \) d) \( \binom{9}{6} (ax)^{9-6} (b)^{6-6} \) **Explanation:** To find the 7th term in the binomial expansion of \((2x + y)^9\), we can use the general term formula in the binomial theorem: \[ T_{k+1} = \binom{n}{k} a^{n-k} b^k \] Given that \( n = 9 \), \( a = 2x \), and \( b = y \): For the 7th term (\( k = 6 \)), we calculate as follows: \[ T_{6+1} = \binom{9}{6} (2x)^{9-6} (y)^6 \] which simplifies to: \[ \binom{9}{6} (2x)^3 y^6 \] By comparing this with the given options, we find that the correct option is: \[ \boxed{ \binom{9}{6} (2x)^{9-6} (y)^6 } \] (\(Note: This is both option (a) and option (c).\)) For deeper understanding, students can refer to the binomial theorem and practice expanding binomials for a variety of expressions.
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