(3-2x)^2+3x+(3x)^2-5x-x^2-7
=9-12x+4x^2+3x+9x^2-5x-x^2-7
=12x^2-14x+2
当x=-1/2时,原式=12.
由12x^2-14x+2=-1得：x=[7+3^(1/2)]/12或x=[7-3^(1/2)]/12