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2(x+y)-3(x+2)=2 3(x-y)+2(y+2)=2x-1 2x+2y-3x-6=2 3x-3y+2y+4=2x-1 -x +2y=8 x +y=-5 + --------------------------- 0 3y=3 y=1 x+y=-5 x+1=-5 x=-5-1 x=-6 y=1 x=-6 b) x+1/2y=7/2 x-y=-1 / * (-1) x + 1/2y= 7/2 -x + y= 1 + ====================== 0 1,5y=4,5 y=3 x-y=-1 x-3=-1 x=-1+3 x=2 y=3 x=2 c) 7/x+2y=5/2x+y /* (x+2y) 5/3x+2=7/y+4 7=5(x+2y)/2x+y /*(2x+y) 5/3x+2=7/y+4 7(2x+y)=5x+10y 5/3x+2=7/y+4 14x+7y=5x+10y 5/3x+2=7/y+4 9x=3y x=1/3y 5 7 --------- = ---------------- 3*1/3+2 y+4 5 7 --- = ------- / *3 3 y+4 5= 21/y+4 5y+20=21 5y=21-20 5y=1 y=1/5 x=1/3*1/5 x=1/15 y=1/5