原式=2(x²+3x/2-1/2)
=2(x²+3x/2+9/16-9/16-1/2)
=2[(x+3/4)²-17/16]
=2[(x+3/4)²-(√17/4)²]
=2(x+3/4+√17/4)(x+3/4-√17/4)