Answer:
-66 x^9 y^3
Step-by-step explanation:
(r + 1)th term of (a + b)^n = nCr a^(n-r) b^r
so the 4th term of (x - y)^12
= 12C2 x^(12-3) (-y)^3
= 66 x^9 (-y)^3
= -66 x^9 y^3 (answer)
