<p>In the expansion of<img alt="\[\left(1 + x + x^2 + \cdots + x^{27}\right)\left(1 + x + x^2 + \cdots + x^{14}\right)^2,\]" height="25" src="https://latex.artofproblemsolving.com/e/4/2/e42212799afc8b50d066ff0471255746cf718dec.png" width="391" />what is the <a href="https://artofproblemsolving.com/wiki/index.php/Coefficient" title="Coefficient">coefficient</a> of <img alt="$x^{28}$" height="15" src="https://latex.artofproblemsolving.com/5/6/c/56cf328af9579c7a405a8692453b578ef97f4fa4.png" width="23" />?</p>

Question No: 236

In the expansion of $\left(1 + x + x^2 + \cdots + x^{27}\right)\left(1 + x + x^2 + \cdots + x^{14}\right)^2,$ what is the coefficient of $x^{28}$ ?

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Tags: Algebra

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