a) x=3-3y 3-3y-y=5 x=3-3y -4y=2 x=3-3y y=-½ x=1½ y=-½
5y=2 x+y=2⅖ y=2/5 x+2/5=2 2/5 x=2 c 4y-x=6 17y=0 4y-x=6 y=0 0-x=6 x=-6 a) x+3y=3 x-y=5 x=3-3y x-y=5 x=3-3y 3-3y-y=5 x=3-3y -4y=2 x=3-3y y=-1/2 x=3-3*(-1/2) x=3/2 2x-y=10 x+5y=-17 x=-17-5y 2x-y=10 x=-17-5y 2(-17-5y)-y=10 x=-17-5y -34-11y=10 x=-17-5y -11y=44 x=-17-5y y=-4 x=-17-5(-4) x=3
5y=2 | :5 x+y=2,4 y=0,4 x=2,4-0,4 y=0,4 x=2 4y-x=6 17y=0 |:17 4y-x=6 y=0 x=-6 y=0 a=b 2a+b=9 a=b 2a+a=9 a=b 3a=9|:3 a=b a=3 b=a a=3 b=3 a=3 ------------------------------------------- x+3y=3 x-y=5 x+3y=3 x=5+y 5+y+3y=3 x=5+y 4y=-2 |4 x=5+y y=-½ x=5+(-½) y=-½ x=4½ 2x-y=10 x+5y=-17 2x-y=10 x=-17-5y 34-10y-y=10 x=-17-5y -11y=44|:(-11) x=-17-5y y=-4 x=-17+20 y=-4 x=3
