Find the 8th term in the expansion (x^2 - 9) ^9.

-172,186,884x^4.

Step-by-step explanation:

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

So the 8th term of (x^2 - 9) ^9 =

(7 + 1) th term

= 9C7 (x^2) ^ (9-7) (-9) ^7

= 36 * (x^2) ^2 * - 4782969

= - 172186884x^4.