原式=8(x²+5x/4+1/4)
=8(x²+5x/4+25/64-25/64+1/4)
=8[(x+5/8)²-9/64]
=8(x+5/8+3/8)(x+5/8-3/8)
=2(x+1)[4(x+1/4)]
=2(x+1)(4x+1)