Question

{3x+y=7
9x-4y=-7 помогите плизз

Answer 1

3x+y=7 *(-3)

9x-4y=-7

 

-9х -3у = -21

9х-4у = -7

 

-7у = -28

у=4

 

3х +4=7

3х = 3

х=1

Answer 2

$left { {{3x+y=7} atop {9x-4y=-7}} right. left { {{y=7-3x} atop {9x-4(7-3x)=-7}} right.left { {{y=7-3x} atop {9x-28+12x=-7}} right. left { {{y=7-3x} atop {21x=21}} right.left { {{y=4} atop {x=1}} right.$

Ответ:(1,4)