2. .............=у² -2у -8+9 - 6у+у² -98+2у²=4у² - 8у - 97
3.
..........=(7^15)/(7^13 *7²)=(7^15)/(7^15)=1
4.
............=2ху+10х -zy -5z=2x(y+5) - z(y+5)=(y+5)(2x-z)
при х= -2, у= -3, z=4
(-3+5)(2*(-2) - 4)= -2*8= -16
5.
(5х+2)² - (3х+5)²=0
(5х+2 -3х -5)(5х+2+3х+5)=0
(2х-3)(8х+7)=0
2х -3=0
2х=3
х1=1,5
8х+7=0
8х= -7
х2= - 0,875 = - 7/8