a)x+2y = -2 2x-y=1 x=-2-2y 2(-2-2y)-y=1 x=-2-2y -4-4y-y=1 -5y=5 //:5 y=1 x+2 = -2 x=0 x=0 y=1
b.) x+4y=-2 3x-8y=10 x=-2-4y 3(-2-4y)-8y=10 x=-2-4y -6-12y-8y=10 x=-2-4y -20y=4 /: (-20) x=-2-4*(-0,2) y=(-0,2) x=(-1,2) y=(-0,2)
a) x+2y=-2 2x-y=1 x=-2-2y 2*(-2-2y)-y=1 -4-4y-y=1 -5y=1+4 -5y=5 y=-1 x=-2-2*(-1) x=-2+2 x=0 B) x+4y=-2 3x-8y=10 x=-2-4y 3*(-2-4y)-8y=10 -6-12y-8y=10 -20y=10+6 -20y=16 y=-16/20 y=-4/5 x=-2-4*(-4/5) x=-2+16/5 x=6/5 C) x-2y=3 -2x+y=0 x=3+2y -2*(3+2y)+y=0 -6-4y+y=0 -3y=6 y=-2 x=3+2y x=3+2*(-2) x=3-4 x=-1 D) 2x+y=9 5x-4y=3 y=9-2x 5x-4*(9-2x)=3 5x-36+8x=3 13x=3+36 13x=39 x=3 y=9-2*3 y=9-6 y=3 e) 3x-2y=5 2x-y=4 y=-4+2x 3x-2*(-4+2x)=5 3x+8-4x=5 -x=-3 x=3 y=-4+2*3 y=2 f) 2x+9y=-9 -3x+3y=8 2x=-9-9y x=-9/2-9/2y -3*(-9/2-9/2y)+3y=8 27/2+27/2y+3y=8 27/2y+3y=8-27/2 33/2y=-9/2 y=-9/2*2/33 y=-9/33 y=-3/11 x=-9/2-9/2*(-3/11) x=-9/2+27/22 x=-99/22+27/22 x=-72/22 x=-36/11 g) 2x+3y=4 8x-5y=-1 2x=4-3y x=4-3/2y 8*(4-3/2y)-5y=-1 32-12y-5y=-1 -17y=-33 y=33/17 x=4-3/2*(33/17) x=4-99/34 x=136/34-99/34 x=37/34 H) x-y=0 x+y+z=4 x+2y+3z=9 x=y z=4-x-y z=4-x-x z=4-2x x+2x+3*(4-2x)=9 3x+12-6x=9 -3x=-3 x=1 y=1 z=4-2*1 z=2
