1. ..........=25а²-40а+16-6а² -11а+7=19а² - 51а+23
2.
1) ....=5у²(х² -9с²)=5у²(х-3с)(х+3с)
2) ....=2(х²+12х+36)=2(х+6)(х+6)=2(х+6)²
3.
у=kx+b
A (0; -6)
B (3; 0)
-6=k*0+b
b= -6
0=3k+b
0=3k-6
3k=6
k=2
b= -6, k=2
4.
2х+у=3 ( *5)
3х-5у=37
10х+5у=15
3х-5у=37
2х+у=3
13х=52
2х+у=3
х=4
у=3-2*4
х=4
у= -5
х=4
(4; -5)