№9
1)
5m+2 - 5m-2 =(5m+2)(5m+2) - (5m-2)(5m-2)= 25m²+10m+10m+4-25m²-4+10m+10m
5m-2 5m+2 (5m-2)(5m+2) (5m-2)(5m+2)
⇒ 40m
(5m-2)(5m+2)
2) 40m ÷ 20m = 40m × -3(25m²-4) = - 6
(5m-2)(5m+2) 12-75m² 25m²-4 20m
1) 2х+1 - 2х-1 = (2х+1)(2х+1) - (2х-1)(2х-1) = 4х²+2х+2х+1-4х²+2х+2х-1 = 8х
2х-1 2х+1 4х²-1 4х²-1 4х²-1
2) 8х ÷ 2х = 8х × 3(2х+1) = 12х
4х²-1 6х+3 (2х-1)(2х+1) 2х 2х-1
№ 10
х+у= 2 ⇒ х=2-у
2х²-ху=65 ⇒ 2(2-у)² -у(2-у)=65 ⇒ 8-8у+2у²-2у+у²=65 ⇒3у²-10у-57=0
Д= 10² -4 *3 *(-57)= 100+684=784=28²
у1= (10-28)/2*3=-18/6=-3 у2= (10+28)/6=38/6
х1= 2- (-3)=5 х2= 2- 38/6= (12-38)/6=-26/6=-13/3