-3(2x+y)=6x-30 2y-5(x+y)=-9 - 12x - 3y = - 30/* (- 1) - 5x - 3y = - 9 12x-5x+3y-3y=30-9 7x=21/ :7 x = 3 x=3 -5*3-3y=-9 x=3 -3y=6/-3 x=3 y= -2 2(x+y)+3=3(x+2y)-7 -(x+2)=6y+2x-10 2x+2y-3x-6y=-7-3 -x-2x-6y=-10+2 -x - 4y = - 10/ *( - 3) -3x - 6y = - 8 3x-3x+12y-6y=30-8 6y=22 /:6 y = 11/3 -x - 4*11/3 = - 10 y=11/3 - x = - 10 + 14 2/3 y = 11/3 x = - 4 2/3 y= 11/3
a) -3(2x+y)=6x-30 2y-5(x+y)=-9 -6x-3y=6x-30 2y-5x-5y=-9 -3y=12x-30 |:(-3) -3y-5x=-9 y=-4x+10 -3(-4x+10)-5x=-9 y=-4x+10 12x-30-5x=-9 y=-4x+10 7x=21 |:7 x=3 y= -4*3+10 x=3 y=-2 b) 2(x+y)+3=3(x+2y)-7 -(x+2)=6y+2x-10 2x+2y+3=3x+6y-7 -x-2=6y+2x-10 2x-3x+2y-6y=-10 -x-2x-6y=-8 -x-4y=-10 -3x-6y=-8 x=-4y+10 -3(-4y+10)-6y=-8 x=-4y+10 12y-30-6y=-8 x=-4y+10 6y=22 |:6 x=-4y+10 y=11/3 x=-4*(11/3)+10 y=11/3 x=-44/3 + 30/3 y=11/3 x=-14/3 y=11/3
