Show that the term containing x3 does not exist in the expansion of (3x-1+2x)8.

Dear Student ,
Please find below the solution to the asked query :

Assuming that question is3x - 12x8Now,General term isTr+1=cr8 3x8-r -12xr=cr8 . 38-r . x8-r . -12r 1xr=cr8 . 38-r . x8-r . -12r x-r=cr8 . 38-r . x8-2r . -12rFor x38-2r=3-2r=3-8-2r=-5r=52r can only have integral value.So , there is no value of r for term x3 .Thus, x3 does not exists in the expansion 3x - 12x8 .
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