{2x+y=9 {5x-4y=3 {3x-2y=5 {2x-y=4 {4x-5y=-4 {-2x+3y=1,1 {-2x+y=0 {3x-3y=1 {y+2-(3-x)=0 {x-2=5-(2-y)

{2x+y=9 {5x-4y=3 y = 9-2x 5x-4(9-2x)=3 5x-36+8x=3 13x=39 / :13 x = 3 y = 9-2*3 y = 9-6 y = 3 {3x-2y=5 {2x-y=4 / *(-2) 3x-2y=5 -4x+2y=-4 / + -x = 1 x = -1 2*(-1) - y = 4 -2-y = 4 -y = 6 y = -6 {4x-5y=-4 {-2x+3y=1,1 / *2 4x-5y=-4 -4x+6y=2,2 / + y = -1,8 -2x+3*(-1,8)=1,1 -2x-5,4=1,1 -2x = 6,5 / :(-2) x = -3,25 {-2x+y=0 {3x-3y=1 y = 2x 3x-3*2x=1 3x-6x=1 -3x=1 / :(-3) x = - 1/3 y = -2/3 {y+2-(3-x)=0 {x-2=5-(2-y) y+2-3+x=0 x-2=5-2+y y+x = 1 x-y=5 / + 2x = 6 / :2 x = 3 y = 1-x y = -2

a) 2x+y=9|*4 5x-4y=3 8x+4y=36 5x-4y=3 13x=39 x=3 2*3+y=9 y=9-6 y=3 b) 3x-2y=5 2x-y=4|*(-2) 3x-2y=5 -2x+2y=-8 x=-3 3*(-3)-2y=5 -2y=14 y=-7 c) 4x-5y=-4|*3 -2x+3y=1,1|*5 12x-15y=-12 -10x+15y=5,5 2x=-6,5 x=-3,25 4*(-3,25)-5y=-4 -5y=9 y=-1,8 d) -2x+y=0|*3 3x-3y=1 -6x+3y=0 3x-3y=1 -3x=1 x=-1/3 -2*(-1/3)+y=0 y=-2/3 e) y+2-(3-x)=0|*2 x-2=5-(2-y)|*2 2y+4-6-2x=0 2x-4=10-4-2y -2x+2y=2|:2 2x+2y=10 -x+y=1 2x+2y=10 y=1+x 2x+2(1+x)=10 2x+2+2x=10 4x=8 x=2 y=1+2 y=3