Find the 4th term of the expansion of (2a-b) ^7

-560a^4b^3.

Step-by-step explanation:

For a binomial expansion:

(r + 1) th term of (a + b) ^n = nCr a^ (n-r) b^r.

So the 4th term of (2a - b) ^7

= (3 + 1) th term = 7C3 (2a) ^ (7-3) (-b) ^3

= 35 * 16a^4 * - b^3

= - 560a^4b^3 (answer).