13/7=26/14=130/70=104/56
80/120=8/12=2/3=10/15
30/48=5/8=10/16=15/24
X=r*cos(fi)
y=r*sin(fi)
dx*dy*dz -> r*dr*dfi*dz
V=integral dx*dy*dz =integral r*dr*dfi*dz =integral (r*dr) * integral (dfi) * integral (dz)=...
integral [0;1] (r*dr) = r^2/2 [0;1] = 1/2
integral [0;2*pi] (dfi) = fi [0;2*pi] = 2*pi
integral [a;b] (dz) = z [a;b] = b-a
V=...=(1/2) * (2*pi) * (b-a) = pi*(b-a)
2/5у=7/15+1
2/5у=1 целых 7/15
у=22/15:2/5
у=22/15•5/2
у=22/6
у=3целых2/3
103/11 = 9 4/11
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18-8=10,..................................