七年级上数学启东作业P48页15题
\u542f\u4e1c\u4f5c\u4e1a\u6570\u5b66\u4e03\u5e74\u7ea7\u4e0a34\u9875\u7b2c15\uff081)\u9898(-1)\u7684N+1\u6b21\u65b9*N
1/2+1/5+1/8+1/11+1/20+1/41+1/110+1/1640=1\uff0c
\u5219\uff1a-1/2-1/5-1/8+1/11-1/20-1/41+1/110+1/1640
=-1+2*[(1/11)+(1/110)+(1/1640)]
=-1+2*(165/1640)
=-131/164
(2)原式=2(x+1)-3(3-x)+(2x+4)=2x+2-9+3x+2x+4=7x-3
当-1<X<3时,化简:(X+1)-(X-3)=(X+1)+(X-3)=2[x-1]
当-1<X<3时,化简:2(X+1)-3(X-3)+(2X+4))=3[x-1]
2[x-1]
绛旓細瑙o細锛1锛夊師寮=(x+1)-(3-x)=x+1-3+x=2x-2 (2)鍘熷紡=2(x+1)-3(3-x)+(2x+4)=2x+2-9+3x+2x+4=7x-3 鍙傝冭祫鏂欙細鍚笢浣滀笟鏈瓟妗