(1).3b²-(a²+b²）-b²
=b²-a²
(2).x+(2x-1)-(3/x+3)
=3/8x-4
(3).-2(ab-3a²)+(5ab-a²）
=3ab+5a²
(4).2a²-2/1（ab+a²）-8ab
=2/3a²-2/17ab
(5).-(b-4)+4(-b-3)
=-5b-8
(6).题目略
=3/2x²-6/1y²-2/1y+3/1x
(1).3b²-(a²+b²）-b²
=b²-a²
(2).x+(2x-1)-(3/x+3)
=3/8x-4
(3).-2(ab-3a²)+(5ab-a²）
=3ab+5a²
(4).2a²-2/1（ab+a²）-8ab
=2/3a²-2/17ab
(5).-(b-4)+4(-b-3)
=-5b-8
(6).题目略
=3/2x²-6/1y²-2/1y+3/1x