[tex]-3x(x+4)+15=6-4x[/tex]
[tex]-3x^2-12x+15=6-4x[/tex]
[tex]-3x^2-12x+4x+15-6=0[/tex]
[tex]-3x^2-8x+9=0[/tex]
this is the form
[tex]ax^2+bx+c=0[/tex]
with a=-3, b=-8 and c=9
the solutions are
[tex]x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}[/tex]
put a, b and c we have
[tex]x=\frac{-4\pm \sqrt{43}}{3}[/tex]
