В2. 25у²+20ху+4х² = (5у)² + 2 · (5у · 2х) + (2х)² = (5у + 2х)² ;
В3. -6х³- 3 (х³ - 1)² = -6х³ - 3 (х⁶ - 2х³ + 1) = -6х³ - 3х⁶ + 6х³ - 3 = -3х⁶ - 3 ;
В4. (х -1)(х +1) - х(х-2)=0.
х² + х - х -1 -х² + 2х = 0
-1 + 2х =0
2х - 1=0
х = 1/2
х = 0,5
В5. (5а - 7b)² + 70ab = 25a² - 70ab + 49b² + 70ab = 25a² + 49b² = (5a+7b)²