The general term of multinomial expansion is
α!β!γ!6!(1)α\left(2^{\frac{1}{3}}\right)^\beta
(321)γ
For terms to be rational
3∣β and
2∣γ<tableclass="qx−match−listqx−match−table"border="1"cellpadding="6"cellspacing="0"><tr><td>β</td><td>γ</td><td>α</td><td>Term</td></tr><tr><td>0</td><td>0</td><td>6</td><td>1</td></tr><tr><td>0</td><td>2</td><td>4</td><td>15.3=45</td></tr><tr><td>0</td><td>4</td><td>2</td><td>15.32=135</td></tr><tr><td>0</td><td>6</td><td>0</td><td>1.33=27</td></tr><tr><td>3</td><td>0</td><td>3</td><td>20.2=40</td></tr><tr><td>3</td><td>2</td><td>1</td><td>60.2.3=360</td></tr><tr><td>6</td><td>0</td><td>0</td><td>1.4=4</td></tr></table>\Rightarrow
Sumofrationalterms=1+45+135+27+40+360+4=612