~Invisibles~

`0.6x(x-0.5)-0.3(2x+1.3)=0.38`

`=> 0.6x^2-0.3x-0.6x-0.39=0.38`

`=> 0.6x^2-0.9x-0.39-0.38=0`

`=> 0.6x^2-0.9x-0.77=0`

`=> x=[45+sqrt6645]/60` hoặc `x=[45-sqrt6645]/60`