!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
По формуле x=-b:2*a; потом ответ подсатляешь в y=....
6x²+bx-7=0, x=1/3
6(1/3)²+b/3-7=0
6/9+b/3-7=0
2/3+b/3-7=0
2+b-21=0
b-19=0
b=19
D=361+168=529, √D=√529=23
x1=(-19+23)/12=4/12=1/3
x2=(-19-23)/2=-42/2=-21
Otvet: b=19
<span><span>4/5÷0,8
×(-1,25)÷(0,64-1/25)-1,2×(-0,5)
</span></span><span><span><span>
1)
0,64-1/25=64/100-1/25=16/25-1/25=15/25=3/5
</span><span>
2) 4/5:0,8=4/5:4/5=1
</span><span>
3) 1*(-1,25)=-1,25
</span><span>
4) -1,25:3/5=-1
1/4*5/3=-5/4*5/3=-25/12
</span><span>
5) 1,2*(-0,5)=-0,6=-3/5
</span><span>
6)
-25/12-(-3/5)=-25/12+3/5=-125/60+36/60=-89/60=-1 29/60
</span></span></span>
Х=2-у
2(2-у)²+ у(2-у)+у²=8
2(4-4у+у²)+2у-у²+у²=8
8-8у+2у²+2у-у²+у²=8
2у²-6у=0
2у(у-3)=0
2у=0; у-3=0
у=0; у=3
х=2-0=2; х=2-3=-1