The term independent of x  in the expansion of (x−3x2)18  is

Given  expansion  (x−3x2)18  We know that rth  term in the expansion of (x+a)n isTr+1=nCr xn−r ar then  Tr+1= 18Crx18−r(−3x2)r Tr+1= 18Cr x18−r (−3)r (x−2)r        = 18Cr (−3)r x18−3r...................(1)  And this will be Without x  only if x18−3r compare with x0  term independent of x  in the expansion⇒x18−3r=x0 ⇒18−3r=0  ∵r=6  in Eqn (1)We get 18C6 (−3)6 x18−18 ∵ 18C6 36