The exponent of power of x  occurring in the 7th  term of expansion of (3x2−87x)9  is

Given expansion is(3x2−87x)9   We have general term in the expansion (x+a)n (∴  Tr+1= nCr xn−r (a)r  be the expansion of (x+a)n)  7th  term of expansionT7=T6+1= 9C6(3x2)9−6 (−87x)6 T7=T6+1=  9C6(32)3(−87)6x−3  (∴xaxb=xa−b)  The exponent of power of x  be the −3 (power of x )