Question

What is the third term in the expansion of (x-3y)^4

Answer 1

`(x - 3y) {}^(4) = x {}^(4) - 4x {}^(3)3y + 6x {}^(2) (3y) {}^(2) - 4x(3y) {}^(3) + (3y) {}^(4) \\ = x {}^(4) - 12x {}^(3)y + 54x {}^(2)y {}^(2) - 108xy {}^(3) + 81y {}^(4) \\ hence \: third \: term \: is \: 54x {}^(2) y {}^(2)`