Y^2+2y+1=(y+1)^2
y = 999
(999+1)^2 = 1000 ^2 = (10^3)^2=10^6=1000000
7:1,75-(3.5:1,25+3.5)+3,4:2,125=7:1,75-(2,8+3,5)+3,4:2,125=7:1,75-6,3+3,4:2,125=4-6,3+1.6=-6,3+5,6=-0,7
x/15 +1=x/10 -1
30*(x/15)+30*1=30*(x/10)-30*1
2x+30=3x-30
2x-3x=-30-30
-x=-60
x=60
60/15=4
60/10=6
4+1=5
6-1=5
60/5=12
O: 12