合并同类项:(1)-3(x2-xy+y2)-2(-x2+xy-2y2) (3)3a2-[7a-(4a-3)-2a2]
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合并同类项:(1)-3(x2-xy+y2)-2(-x2+xy-2y2) (3)3a2-[7a-(4a-3)-2a2]
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感激不尽
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感激不尽
(1)-3(x²-xy+y²)-2(-x²+xy-2y²)
=-3x²+3xy-3y²+2x²-2xy+4y²
=-3x²+2x²+4y²-3y²+3xy-2xy
=-x²+y²+xy
(3)3a²-[7a-(4a-3)-2a²]
=3a²-7a+4a-3+2a²
=3a²+2a²-7a+4a-3
=5a²-3a-3
=x/2-2x+2y²/3-3x/2+y²/3
=(x/2-3x/2-2x)+(2y²/3+y²/3)
=-3x+y²
=a/3-a/2+4b+6c-6c+6b
=a/3-a/2+4b+6b+6c-6c
=-a/6+10
=-3x²+3xy-3y²+2x²-2xy+4y²
=-3x²+2x²+4y²-3y²+3xy-2xy
=-x²+y²+xy
(3)3a²-[7a-(4a-3)-2a²]
=3a²-7a+4a-3+2a²
=3a²+2a²-7a+4a-3
=5a²-3a-3
=x/2-2x+2y²/3-3x/2+y²/3
=(x/2-3x/2-2x)+(2y²/3+y²/3)
=-3x+y²
=a/3-a/2+4b+6c-6c+6b
=a/3-a/2+4b+6b+6c-6c
=-a/6+10
因式分解:x2-9a2+12a-4;x2y+3xy2-x-3y;1-x2-2xy-y2;3a2+2b-2ab-3a;x2
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