7а-10=2-4а
7а+4а=2+10
11а=12
а=12/11
2.6-0.2b=4.1-0.5b
-0.2b+0.5b=4.1-2.6
0.3b=1.5
b= 5
0.8-y=3.2+y
-2y=3.2-0.8
-2y=2.4
y= -1.2
2x-0.7x=0
1.3х=0
х=0
.....................................................
Y=0
x²+11x+28=0
D=121-102=9(3)
x=(-11+3)/2=-4
x=(-11-3)/2=-7
x=0
y=0+0+28
y=28