因式分解:(x+2y)(3x2-4y2)-(x+2y)2(x-2y)=________.
1.21a3b-35a2b3=_________．
2.3x2yz+15xz2-9xy2z=__________．
3.x2-2xy-35y2=(x-7y)()．
4.2x2-7x-15=(x-5)()．
5.20x2-43xy+14y2=(4x-7y)()．
6.18x2-19x+5=()(2x-1）
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