D=33-37=-4
A₂₀=A₁+19d=37+19*(-4)=37-76=-39
S₂₀=<u>(A₁+A₂₀)*20</u> = (37-39)*10=-2*10=-20
2
Ответ: -20
69 - (169 - 26 + y2) = -y2
69 - 169 + 26y - y2 = -y2
69 - 169 + 26y = 0
-100 + 26y = 0
26y = 100
y = 50/13
А)х=1,у=2 Б)х=0,у=2;7у-14=0;7у=14;у=2; х-4+4=0;х=0
4х-4=0
4х=4
х=1
1-у+1=0
у=2