{2x-y=10 {x+5y=-17 {4a-2=b {3a+7b=1,5 {6x-3y=9 {x+5y=-9,5

{2x-y=10 {x+5y=-17 -> x= -17-5y 2(-17-5y)-y=10 -34-10y-y=10 -11y=10+34 -11y=44 /:(-11) y=4 {y=4 {x=-17-5y x=-17-5*4 x= 3 {y=4 {x=3

{2x-y=10 {x+5y=-17 /*(-2) 2x-y=10 -2x-10y=34 2x-2x-y-10y=10+34 -11y=44 /(-11) y=-4 2x-y=10 2x-(-4)=10 2x=4+10 2x=14/2 x=7 x=7 y=4 {6x-3y=9 {x+5y=-9,5 /*(-6) 6x-3y=9 -6x-30y=57 6x-6x-3y-30y=9+57 -33y=66 /(-33) y=-2 {6x-3y=9 6x-3(-2)=9 6x+6=9 6x=-6+9 6x=3/6 x=1/3 x=1/3 y=-2

{2x-y=10 / ×5 {x+5y=-17 {10x-5y=50 {x+5y= -17 11x= 33/:11 x= 3 10x-5y=50 -5y=50-10x -5y=50-10×3 -5y= 50-30 -5y=20 /:(-5) y= -4 {x=3 {y=-4 {4a-2=b {3a+7b=1,5 {4a-b=2 /×7 {3a+7b=1,5 {28a-7b=14 {3a+7b= 1,5 31a= 15,5 /:31 a=0,5 3a+7b= 1,5 7b= 1,5-3a 7b= 1,5 -3×0,5 7b= 1,5-1,5 7b= 0 / :7 b= 0 {a=0,5 {b=0 {6x-3y=9 /×5 {x+5y=-9,5 /×3 {30x-15y= 45 {3x+15y= -28,5 33x= 16,5 /:33 x= 0,5 30x-15y=45 -15y=45-30x -15y= 45-30×0,5 -15y= 45-15 -15y= 30 /:(-15) y= -2 {x=0,5 {y=-2