[m](\frac{u}{v})`=\frac{u`\cdot v-u\cdot v`}{v^2}[/m]
u=6x+5
v=4-3x
[m]y`=\frac{(6x+5)`\cdot(4-3x)-(6x+5)\cdot (4-3x)`}{(4-3x)^2}[/m]
[m]y`=\frac{6\cdot(4-3x)-(6x+5)\cdot (-3)}{(4-3x)^2}[/m]
[m]y`=\frac{24-18x+18x+15}{(4-3x)^2}[/m]
[m]y`=\frac{39}{(4-3x)^2}[/m]