(х+у)^2=-0,7^2+2 ×(-0,7) ×(-1,2)+(-1,2)^2=3.61
A1 = 2
S5 = - 40
n = 5
(2a1 + d(n - 1))/2 * n = - 40
(2*2 + 4d)/2*5 = 40
(4 + 4d)*2,5 = 40
4d + 4 = 16
4d = 12
d = 3
A) 4*(c+5)=c+2
4c+5=c^2+4c+
c^2-1=0
c=+1 и c=-1
Б)d^2-2d+1=d+5
d^2-3d-4=0
D=9+16=25
d1=(3+5)/2=4
d2=(3-5)/2=-1
Г) 3u+1-4-u+1=0
2u-2=0
2u=2
u=1
Х-2 / 5-х > 0
х-2 > 0 5 - x ≠ 0
<u>x > 2 </u> x ≠ 5
Ответ: (2; + <span>∞)</span>