D = 8, S8 = 200
S = 2a1 + d(n - 1) * n / 2
200 = 2a1 + 8(8-1) * 8 / 2
200 = 2a1 + 448 / 2
400 = 2a1 + 448
-48 = 2a1
a1 = -24
20:0
(5+5) : (3-3)
(34-6) : (34+6-40)
(41+14) : (11+3-14)
(3+9) : (4+5-9)
25-4x^2+4xy-y^2=25-(4x^2-4xy+y^2)=25-(2x-y)^2=(5+2x-y)(5-2x+y)
(√0,36/6)-1=(0,6/6)-1=0,1-1=-0,9