-4(x+2y)²+9(2x-y)²
=9(2x-y)²-4(x+2y)²
=[3(2x-y)+2(x+2y)][3(2x-y)-2(x+2y)]
=(8x+y)(4x-7y)再问一道题..计算(2×10²)³×(3×10³)²-(4×10^4)³=4×10^6×9×10^6-64×10^12=36×10^12-64×10^12=-28×10^12=-2.8×10^13