化简(1) 7-3x-4x2+4x-8x2-15 (2) 2(2a2-9b)-3(-4a2+b)
(3) 8x2-[-3x-(2x2-7x-5)+3]+4x
先化简,后求值;
(1)(5x-3y-2xy)-(6x+5y-2xy),其中,
(2)若,求3a2b-[2ab2-2(ab-1.5a2b)+ab]+3ab2的值;
化简(1) 7-3x-4x2+4x-8x2-15 (2) 2(2a2-9b)-3(-4a2+b)
(3) 8x2-[-3x-(2x2-7x-5)+3]+4x
先化简,后求值;
(1)(5x-3y-2xy)-(6x+5y-2xy),其中,
(2)若,求3a2b-[2ab2-2(ab-1.5a2b)+ab]+3ab2的值;