a) 2(2x-y)+3(x+3y)=42 5(x+3y)-8(2x-y)=-32 4x-2y+3x+9y=42 5x+15y-16x+8y=-32 7x=-7y+42 /:7 23y=11x-32 x=-y+6 23y=11(-y+6)-32 x=-y+6 23y=-11y+34 x=-y+6 34y=34 /:34 x=-y+6 y=1 x=5 y=1 b) 10(y+2)+3(x-5)=x-5 25(y+2)+3(x-5)=-10 10y+20+3x-15=x-5 25y+50+3x-15=-10 2x=-10y-10 /:2 25y=-3x-45 x=-5y-5 25y=-3(-5y-5)-45 x=-5y-5 25y=15y+15-45 x=-5y-5 25y=15y-30 x=-5y-5 10y=-30 /:10 x=-5y-5 y=-3 x=10 y=-3
a) 2(2x-y)+3(x+3y)=42 5(x+3y)-8(2x-y)=-32 4x-2y+3x+9y=42 5x+15y-16x+8y=-32 7x+7y=42|:7 -11x+23y=-32 x=6-y -11(6-y)+23y=-32 -66+11y+23y=-32 34y=34 y=1 x=6-1 x=5 b) 10(y+2)+3(x-5)=x-5 25(y+2)+3(x-5)=-10 10y+20+3x-15=x-5 25y+50+3x-15=-10 2x+10y=-10|:2 3x+25y=-45 x=-5-5y 3(-5-5y)+25y=-45 -15-15y+25y=-45 10y=-30 y=-3 x=-5-5*(-3) x=-5+15 x=10
