6.
[tex]2x^{3}-3xy = \frac{x}{2}\cdot4x^{2}-\frac{x}{2}\cdot6y = \underline{\frac{x}{2}(4x^{2}-6y)}\\\\Odp. \ B.[/tex]
15.
a)
[tex]2 \ km = 20 \ 000 \ dm=2\cdot10^{4} \ dm\\\\13 \ mm = 0,013 \ m = 1,3\cdot10^{-2} \ m\\\\23 \ cm = 0,00023 \ km = 2,3\cdot10^{-4} \ km[/tex]
b)
[tex]37 \ kg = 3 \ 700 \ dag = 3,7\cdot10^{3} \ dag\\\\56 \ g = 0,056 \ kg = 5,6\cdot10^{-2} \ kg\\\\81 \ g = 0,000081 \ t = 8,1\cdot10^{-5} \ t[/tex]
c)
[tex]2 \ m^{2} = 2\cdot100 \ dm^{2}=200 \ dm^{2} = 2\cdot10^{2} \ dm^{2}\\\\7,1 \ m^{2} = 71 \ 000 \ cm^{2}=7,1\cdot10^{4} \ cm^{2}\\\\4,5 \ mm^{2} = 0,0000045 \ m^{2} = 4,5\cdot10^{-6} \ m^{2}[/tex]