3(2x-y)-1=3x+2y
6x-3y-1-3x-2y=0
3x-3y-1-2y=0
3x-5y-1=0
y=-(-3*x+1)/5
y=0.6x-0.2
4(х-2у)+4=2х+у-1
4(х-2*(0.6x-0.2))+4=2х+(0.6x-0.2)-1
4*(x-(1.2x-0.4))+4-2x-(0.6x-0.2)+1=0
4*(x-1.2x+0.4)+4-2x-(0.6x-0.2)+1=0
4*(-0.2x+0.4)+4-2x-(0.6x-0.2)+1=0
-0.8x+1.6+4-2x-(0.6x-0.2)+1=0
-0.8x+5.6-2x-(0.6x-0.2)+1=0
-2.8x+5.6-(0.6x-0.2)+1=0
-2.8x+5.6-0.6x+0.2+1=0
-3.4x+5.6+0.2+1=0
-3.4x+5.8+1=0
-3.4x+6.8=0
x=6.8/3.4
x=2
3(2x-y)-1=3x+2y
3(2*2-y)-1=3*2+2y
3*(4-y)-1-3*2-2y=0
12-3y-1-3*2-2y=0
11-3y-3*2-2y=0
11-3y-6-2y=0
5-3y-2y=0
5-5y=0
y=5/5
y=1
ответ: x=2; y=1.
Написал как можно подробнее.
3a²-2a-5<0
D=4+60=64
a1=(2-8)/6=-1 U a2=(2+8)/6=5/3
a∈(-1;5/3)
{x1+x2=-a-3⇒3x2+x2=-a-3⇒4x2=-a-3⇒x2=(-a-3)/4
{x1*x2=a²+a+1
3x2*x2=a²+a+1
3x2²=a²+a+1
3*(-a-3)²/16=a²+a+1
16a²+16a+16-3a²-18a-27=0
13a²-2a-11=0
D=4+572=576
a1=(2-24)/26=-11/13
x2=(11/13-3)/4=-2 2/13:4=-28/52=-7/13⇒x1=-21/13
a2=(2+24)/26=1
x2=(-1-3)/4=-1⇒x1=-3