Question

21b^2 - 81c^2
using identity

pls help​

Answer 1

Answer:

hence there is your answer

Step-by-step explanation:

✔ 81^2 = (80 + 1)^2

using (a + b)^2 = a^2 + b^2 + 2ab

✔ (80 + 1)^2

➡ (80)^2 + (1)^2 + 2(80)(1)

➡ 6400 + 1 + 160

➡ 6561