a) x + 1 = 2x-2y -x + y = -3 x + 1 = 2x - 2y y = x - 3 x + 1 = 2x - 2*(x - 3) y = x-3 x + 1 = 2x - 2x - 6 y = x-3 x - 2x + 2x = -3 -1 - 6 y = x - 3 x = -10 y = x - 3 x = -10 y = -10 -3 x = -10 y = -13 2. a) 2x + y = 6 x + y = 4 2x + y = 6/*(-1) x + y = 4 -2x -y = -6 x + y = 4 ------------------ -x = -2/:(-1) x = 2 2x + y = 6 x + y = 4/*(-2) 2x + y = 6 -2x -2y = -8 ------------------------- -y = -2/:(-1) y = 2 b) x + 2y = 2 4x + 2y = 8 x + 2y = 2/*(-4) 4x + 2y = 8 -4x -8y = -8 4x + 2y = 8 -------------------------- -6y = 0/:(-6) y = 0 x + 2y = 2 4x + 2y = 8 x + 2y = 2/*(-1) 4x + 2y = 8 -x -2y = -2 4x + 2y = 8 ------------------- -3x = 6/: (-3) x = -2 c) 2x + 5y = -1 -2x -3y = 5 ---------------- 2y = 4/: 2 y = 2 2x + 5y = -1/*3 -2x -3y = 5/*5 6x + 15y = -3 -10x - 15y = 25 --------------------- -4x = 22/:(-4) x = [latex] frac{22}{4} [/latex] = [latex]5 frac{2}{4} [/latex] = [latex] 5frac{1}{2} [/latex] = 5,5
x+1=2x-2y -x+y=-3 x-2x+2y=-1 -x+y=-3 -x+2y=-1 -x+y=-3 y=x-3 -x+2(x-3)=-1 y=x-3 -x+2x-6=-1 y=x-3 x=-1+6 x=5 y=5-3 y=2 x=5 --------------------------- 2x+y=6 x+y=4 /*-1 2x+y=6 -x-y=-4 x=2 2*2+y=6 4+y=6 y=6-4 y=2 x=2 ------------------- x+2y=2 /* -1 4x+2y=8 -x-2y=-2 4x+2y=8 3x=6 x=2 4*2+2y=8 2y=0 y=0 x=2 --------------------------- 2x+5y=-1 -2x-3y=5 2y=4 y=2 2x+5*2=-1 2x+10=-1 2x=-11 /:2 x= -5,5 y=2 ---------------------------
