1) (9-y)(9+y)=2) (3b-1)(3b+1)=3) (10m-7)(10m+7)=4) (4a-b)(b+4a)=5) (5b-1)(1-5b)=6) (3x-5y)(3x+5y)=7) (13c-10d)(13c+10d)=8) (8m+11n)(11n-8m)=​

1) (9-y)(9+y)= 81 - у²

2) (3b-1)(3b+1)= 9b² - 1

3) (10m-7)(10m+7)= 100m² - 49

4) (4a-b)(b+4a)= 16a² - b²

5) (5b-1)(1-5b)= - (1-5b)(1-5b) = - (1-5b)² = - (1 - 10b + 5b²) = -1 + 10b - 5b²

6) (3x-5y)(3x+5y)= 9x² - 25y²

7) (13c-10d)(13c+10d)= 169c² - 100d²

8) (8m+11n)(11n-8m)=​ 121n² - 64m²