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解方程2.8x=19.32-6.4x5(y-4)-7(7-y)-9=12-3(9-y)

来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/13 05:07:24
解方程
2.8x=19.32-6.4x
5(y-4)-7(7-y)-9=12-3(9-y)
(1)2.8x=19.32-6.4x,
    2.8x+6.4x=19.32-6.4x+6.4x,
         9.2x=19.32,
    9.2x÷9.2=19.32÷9.2,
            x=2.1;
(2)5(y-4)-7(7-y)-9=12-3(9-y),
           5y-20-49+7y-9=12-27+3y,
                  12y-78=3y-15,
               12y-78+78=3y-15+78,
                  12y-3y=3y+63-3y,
                      9y=63,
                   9y÷9=63÷9,
                       y=7.