去括号,在合并同类项.1.8X+2Y+2(5X-2Y) 2.7M+3M+3(M+2N)4.2X²-2[3X-2(-X²+2X-1﹚-4]

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去括号,在合并同类项.1.8X+2Y+2(5X-2Y) 2.7M+3M+3(M+2N)4.2X²-2[3X-2(-X²+2X-1﹚-4]
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去括号,在合并同类项.1.8X+2Y+2(5X-2Y) 2.7M+3M+3(M+2N)4.2X²-2[3X-2(-X²+2X-1﹚-4]
去括号,在合并同类项.1.8X+2Y+2(5X-2Y) 2.7M+3M+3(M+2N)
4.2X²-2[3X-2(-X²+2X-1﹚-4]

去括号,在合并同类项.1.8X+2Y+2(5X-2Y) 2.7M+3M+3(M+2N)4.2X²-2[3X-2(-X²+2X-1﹚-4]
1.8X+2Y+2(5X-2Y)
=8x+2y+10x-4y
=18x-2y
2.7M+3M+3(M+2N)
=10m+3m+6n
=13m+6n
4.2X²-2[3X-2(-X²+2X-1﹚-4]
=2x²-2(3x+2x²-4x+2-4)
=2x²-2(2x²-x-2)
=2x²-4x²+2x+4
=-2x²+2x+4

1.原式=8x+2y+10x-4y=18x-2y;2.原式=7m+3m+3m+6n=13m+6n;4.x^2表示x的平方;原式=2x^2-2(3x+2x^2-4x
+2-4)=2x^2-6x-6x^2+8x+2=-4x^2+2x+2