10-4(2x+5)=6y-13
4y-63=5(4x-2y)+2
4y-63-20x+10y-2=0
14y-65-20x=0
x=0.7y-3.25
3-8x-6y=0
3-8*(0.7y-3.25)-6y=0
3-5.6y+26-6y=0
29-11.6y=0
y=29/11.6y=2.пятых
14*2.5-65-20x=0
-30-20x=0
x=-30/20
x=-1.5
D =144-80=64
√D=8
x=5
x=1
x2+6x+5=0
D=36-20=16
√D=4
x= -5
x= -1
x2+14x+45=0
D=196-180=16
√D=4
x= -5
x= -9
x2-6x-7=0
D=36+28=64
√D=8
x=7
x= -1