C) {2x-3y=-5 {-x+5y=6 | *(-1) {x=5y-6 {2(5y-6)-3y=-5 10y-12-3y=-5 7y=12-5 y=7 x= 5*7-6 {x= 29 {y=7 D) {3x-3y+3=0 {x+½y-2=0 {x=2-½y {3(2-½y)-3y+3=0 6-1½y-3y+3=0 6+3=4½y y=2 x=2-½*2 {x=1 {y=2 E) {4x-2y=6 {3x+6y=12 | /3 x+2y=4 x=4-2y 4(4-2y)-2y=6 16-10y=6 10=10y y=1 x=4-2 {x=2 {y=1 F) {3x-4y=14 {-2x+7y=-18 | /(-2) x-3,5y=9 x=9+3,5y 3(9+3,5y)-4y=14 27+6,5y=14 6,5y=14-27 6,5y=-13 y=-2 x=9+3,5y*(-2) {x=2 {y=-2
C) {2x-3y=-5 {-x+5y=6 2x-3y=-5 -x=6-5y I * (-1) 2x-3y=-5 x=-6+5y 2(-6+5y)-3y=-5 x=-6+5y -12+10y-3y=-5 x=-6+5y 10y-3y=-5+12 x=-6+5y 7y=7 /:7 x=-6+5y y=1 x=-6+5y y=1 x=-6+5*1 y=1 x=-6+5 y=1 x=-1 D) {3x-3y+3=0 {x+½y-2=0 3x-3y+3=0 x=-1/2y+2 3(-1/2y+2)-3y+3=0 x=-1/2y+2 -1,5y+6-3y+3=0 x=-1/2y+2 -1,5y-3y=-6-3 x=-1/2y+2 -4,5y=-9 /:(-4,5) x=-1/2y+2 y=2 x=-1/2*2+2 y=2 x=1 E) {4x-2y=6 {3x+6y=12 -2y=6-4x /:(-2) 3x+6y=12 y=-3+2x 3x+6y=12 y=-3+2x 3x+6(-2+2x)=12 y=-3+2x 3x-12+12x=12 y=-3+2x 3x+12x=12+12 y=-3+2x 12x=24 /12 y=-3+2x x=2 y=-3+2*2 x=2 y=-3+4 x=2 y=1 x=2
