Resposta:
[tex]>\frac{y^{12} \ . \ y^{16} \ . \ y^{21}}{y^{22} \ . \ y^{40}} \\\\[/tex]
[tex]=\frac{y^{16}y^{21}}{y^{10}y^{40}} \\\\[/tex]
[tex]=\frac{y^6y^{21}}{y^{40}}[/tex]
[tex]=\frac{y^{21}}{y^{34}}[/tex]
[tex]=\frac{1}{y^{13}}[/tex]
