①12x2+8x-3xy-2y
=4x(3x+2)-y(3x+2)
=(3x+2)(4x-y)
②16a^4-b^8
=(4a²)²-(b^4)²
=(4a²+b^4)(4a²-b^4)
=(4a²+b^4)(2a+b²)(2a-b²)
③-3xy-9y²-1/4x²
=-1/4(36y²+12xy+x²)
=-1/4(x+6y)²
或③-3xy-9y²-1/4x²
=-(9y²+3xy+1/4x²)
=-(1/2x+3y)²
④12x²＋8x－3xy-2y
=4x(3x+2)-y(3x+2)
=(3x+2)(4x-y)