数学题求解······好了,加分·······每一步写清楚
1.(3x+9)(6x+8)
2.(12x²y-2xy+y²)*3xy
3.(13a²b³)*(-15a²b²)
4.(3mn+1)(3mn-1)-8m²n²
5.(x+2)²-(x+1)(x-1)
6.(-2m-1)(3m-2)
每一步写清楚