1. 7x+3y=-1 / × 5 2x+5y=14 / × (-3) 35x+15x=-5 -6x-15x=-42 35x=-5 -6x=-42 29x=-47 x=1,62 2. 4(x-2)-y=1 2x-4y=8 4x-8-y=1 2x-4y=8 / × (-2) 4x-8-y=1 -4x+8y=-16 -y=9 8y=-16 y=-2 3. 5x-y=7 2(x+1)=2y 5x-y=7 / × (-2) 2x-2y=-2 -10x+2y=-14 2x-2y=-2 -8x=-16 x=2 4. 4(x-2)-(y-2)=1 10x+2y=18 4x-8+y+2=1 / × (-2) 10x+2y=18 -8x+16-2y-4=-2 10x+2y=18 -8x=-14 10x=18 2x=4 x=2 5. 6x-9y=6 8x+5y=7/3 / × 3 6x-9y=6 / × (-4) 24x+15y=7 -24x+36y=-24 24x+15y=7 51y=17 y=2,29
1. 7x+3y=-1 |*2 2x+5y=14 |*(-7) 14x+6y=-2 -14x-35y=-98 --------------- -29y=-100|; (-29) y=3,45 7x+10,35=-1 y=3,45 x=1,62 y=3,45 2. 4(x-2)-y=1 2x-4y=8 4x-8-y=1 2x-4y=8 |*-2) 4x-y=9 -4x+8y=-16 ------------ 7y=-7 |:7 y=-1 2x+4=8 y=-1 x=2 y=-1 3. 5x-y=7 2(x+1)=2y 5x-y=7 2x+2=2y 5x-y=7 |*(-2) 2x-2y=-2 -10x+2y=-14 2x-2y=-2 ---------------- -8x=-16 |:(-8) x=2 10-y=7 x=2 -y=-3 |*(-1) x=2 y=3 x=2 4. 4(x-2)-(y-2)=1 10x+2y=18 4x-8-y+2=1 10x+2y=18 4x-y=7 |*2 10x+2y=18 8x-2y=14 10x+2y=18 -------------- 18x=32|:18 x=1,78 4*1,78-y=7 x=1,78 y=-0,12 x=1,78 5. 6x-9y=6 8x+5y=7/3
