[tex]\frac{3x+1}{x^{2}}=\frac{x}{5x-1}[/tex]
mnożymy na "krzyż"
[tex]x^{2}\cdot x = (3x+1)(5x-1)\\\\x^{3} = 15x^{2}-3x+5x-1\\\\\underline{x^{3} = 15x^{2}+2x-1}\\\\\boxed{Odp. \ B.}[/tex]
