3) {y-x=-3
{x²-y²=63
y=x-3
x²-(x-3)²=63
x²-x²+6x-9=63
6x=63+9
6x=72
x=12
y=12-3=9
Ответ: х=12у=9
4) ( 3х-х² + 2х ) * (2х²-х-15)=(х(3-х) + 2х ) * (2х²-х-15)=
(х²-6х+9 2х+5) ( (х-3)² 2х+5)
=(-х(х-3) + 2х ) * (2х²-х-15)= (-х + 2х ) * (2х²-х-15)=
( (х-3)² 2х+5) (х-3 2х+5)
=(-х(2х+5)+2х(х-3)) * (2х²-х-15)=(-2х²-5х+2х²-6х) * (2х²-х-15)=
( (х-3)(2х+5) ) ( 2х²-6х+5х-15 )
= -11х * (2х²-х-15)= -11х
2х²-х-15