x.y满足方程组3ax+4y=9-6ax+5y=27,那么3ax+y的值是———

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x.y满足方程组3ax+4y=9-6ax+5y=27,那么3ax+y的值是———
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x.y满足方程组3ax+4y=9-6ax+5y=27,那么3ax+y的值是———
x.y满足方程组3ax+4y=9-6ax+5y=27,那么3ax+y的值是———

x.y满足方程组3ax+4y=9-6ax+5y=27,那么3ax+y的值是———
将ax看成一个值,然后
3ax+4y=27
9-6ax+5y=27
二式联立:
y=72/13,ax=21/13;
代入
3ax+y=135/13.

13分之135

3ax+4y=9 (1)
-6ax+5y=27 (2)
(1)*2+(2)
13y=45
y=45/13
代入(1)
3ax=9-4y=9-180/13=-63/13
3ax+y=-63/13+45/13=-18/13