Question

решить систему уравнений х/3 +7у=13, -5х+1/2у=16

Answer 1

$left { {{frac{x}{3}+7y=13 | cdot3} atop {-5x+frac{1}{2}y=16 | cdot 2}}$

$right. left { {{x+21y=39} atop {-10x+y=32}} right. left { {{x=39-21y} atop {-10(39-21y)+y=32}} right. left { {{x=39-21y} atop {-390+210y+y=32}} right.\\ left { {{x=39-21y} atop {211y=32+390}} right. left { {{x=39-21y} atop {211y=422}} right. left { {{x=39-21y} atop {y=422:211}} right. left { {{x=39-21cdot2} atop {y=2}} right. left { {{x=39-42} atop {y=2}} right.\\ left { {{x=-3} atop {y=2}} right.$

Answer 2

1 уравнение домножим на 3

х+21у=39

-5х+0,5у=16

х=39-21у

-5*(39-21у)+0,5у=16

-195+105у+0,5у=16

105,5у=211

у=2

х=39-42= -3

Ответ: (-3; 2)