2. 外语
  3. 4x-2y=6 -6x+5y=7

4x-2y=6 -6x+5y=7

admin2012-10-19  6
问题 4x-2y=6      -6x+5y=7
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答案 This problem is a little trickier than the first, as you cannot simply change the sign of one of the equations to isolate one of the variables. In this situation, you have to make the coefficients the same through multiplication. Since you know that 4 and 6 both go into 12, use the x term. Multiply the top equation by 3, and the bottom by 2: 12x-6y=18 -12x+10y=14 Add the two equations together (note that the x terms cancel out): 4y=32 y=8 Finally, choose one of the original equations, substitute 8 for y, and solve for x. [*]
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