Đáp án:
Giải thích các bước giải:
$\left \{ {{\frac{2x+3y}{4}-\frac{4x-y}{3}=\frac{35}{4} } \atop {\frac{3x-5y}{3}+\frac{2x+7y}{5}}=-\frac{140}{15}} \right. $
<=> $\left \{ {{\frac{6x+9y}{12}-\frac{16x-4y}{12}=\frac{105}{12}} \atop {\frac{15x-25y}{15}+\frac{6x+21y}{15}=-\frac{104}{15}}} \right.$
<=> $\left \{ {{6x+9y-16x+4y=105} \atop {15x-25y+6x+21y=-104}} \right.$
<=> $\left \{ {{-10x+13y=105} \atop {21x-4y=-104}} \right.$
<=> $\left \{ {{-40x+52y=420} \atop {273x-52y=-1352}} \right.$
<=> $\left \{ {{233x=-932} \atop {21x-4y=-104}} \right.$
<=> $\left \{ {{x=-4} \atop {21.(-4)-4y=-104}} \right.$
<=> $\left \{ {{x=-4} \atop {y=5}} \right.$
Vậy, hệ pt có nghiệm (x;y) = (-4;5)
