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x=6/a或x=-2/aa^2X^2-4aX-12=0即(aX-2)^2=16即①aX-2=4或②aX-2=-4①aX=6所以X=6/a②aX=-2所以X=-（2/a）

是否存在这样的整数a,使方程组3x+4=a,4x+3y=5的解是一对非负数?如果存在,求出它的解,如果不存在，请说明理由...
是否存在这样的整数a,使方程组3x+4=a,4x+3y=5的解是一对非负数?如果存在,求出它的解,如果不存在，请说明理由
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3x+4=a,4x+3y=5x=(a-4)/3y=(31-4a)/9x>=0y>=0所以a-4>=0, 31-4a>=0a>=4, a<=31/4整数a, a=4,5,6,7所以存在整数a=4,5,6,7使方程组3x+4=a,4x+3y=5的解是一对非负数解为{x=0,y=5/3},{x=1/3,y=11/9},{x=2/3,y=7/9},{x=1,y=1/3}
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3x+4y=a 4x+3y=5解为x= (-3a+20)/7y= (4a-15)/7要是解为非负数，则有x= (-3a+20)/7≥0y= (4a-15)/77≥0即为不等式组-3a+20≥04a-15≥0第一个式子解得 a≤20/3第二个式子解得 a≥15/4满足15/4≤a≤20/3 的整数有 4,5,6所以a=4,5,6都为满足条件的a
展开全部由题意知：x=（a-4）/3y=(31-4a)/9又x、y均大于等于0所以（a-4）/3、(31-4a)/9均大于等于则有（a-4）/3大于等于0(31-4a)/9大于等于0解之得：a大于等于4，小于等于7.75所以a的整数值有4\5\6\7
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解方程组得: X=(a-4)/3y=(1-4a)/9令X和Y都大于等于零,成立不等式组.解得:a<=1/4且a>=4无解.
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选择擅长的领域继续答题？
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${item.tagName}
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a减b加2等于0，与4a加2b加2等于12的方程式。怎么解？解：首先写出这个二元一次方程组：a-b+2=0.4a+2b+2=12.对（1）式的方程两边同乘4:4a-4b+8=0减去（2）式：-4b-2b+6=-12-6b=-18b=3.a=3-2=1.
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