Precalculus (6th Edition)

Published by Pearson

Chapter 11 - Further Topics in Algebra - 11.4 The Binomial Theorem - 11.4 Exercises: 10

Answer

$-560x^{4}y^{3}$

Work Step by Step

$n$th term in $\left( a+b\right) ^{k}$ is $\binom k {n-1} a^{k+1-n}b^{n-1}$ So 4th term in $\left( 2x-y\right) ^{7}\Rightarrow \binom 7 3 \left( 2x\right) ^{4}\left( -y\right) ^{3}=-\dfrac {7!}{3!\left( 7-3\right) !}\times 16x^{4}y^{3}=-560x^{4}y^{3}$

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