Question

решить систему уравнений  3(x+y)+1=x+4y и 7-2(x-y)=x-8y

Answer 1

3(x+y)+1=x+4y
7-2(x-y)=x-8y

3x+3y+1-x-4y=0
7-2x+2y-x+8y=0

2x-y+1=0
-3x+10y+7=0

2x-y=-1
-3x+10y=-7

-y=-1-2x
-3x+10y=-7

y=1+2x
-3x+10(1+2x)=-7

-3x+10+20x=-7
17x=-17
x=-1
y=1+2*(-1)
y=1-2
y=-1