http://wenku.baidu.com/link?url=NiljgHFNtbpBH7RNmHdibIJIWFsiQA64wmS4_yvdjbmFlk3nwkhjYT_6NdeVkJS2TDsWOVjYN_6n79x_Z9RHJtUHnZr_GmIRfQlxB504UxG
先把未知数的系数化为一,
2x+4=8 x=2