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计算:
(1)(-x2-5xy+12y2)-(2y2-xy-3x2)
(2)3x-4(x-3y+4z)+5(2x-6y-2z)
(1)-3a2-(-3a2-a+1);
(2)(x2-3x+2)-(3x2-7x-3).
计算:(1)2a2b·3ab2 (2)3x(x2-2x-1) (3) (4)
计算:(1)2a2b·3ab2 (2)3x(x2-2x-1)
(3) (4)