Question

answer the above question


it's factorisation ​

Answer 1

Step-by-step explanation:

$= 81 - (2x - 5y) {}^{2} - 40xy \\ = 81 - (4 {x}^{2} + 25 {y}^{2} - 20xy) - 40xy \\ = 81 - 4 {x}^{2} - 25 {y}^{2} + 20xy - 40xy \\ = 81 - 4 {x}^{2} - 25y {}^{2} - 20xy$

Answer 2

Here is your answer,refer to the attachment.

Last line has the answer.