[latex]a). \ left { {{-x-y=-6} atop {-x+y=2}} ight. + \ ------ \ -2x=-4/:(-2) \ x=2 \ \ -x-y=-6 \ -2-y=-6 \ -y=-6+2 \ -y=-4/*(-1) \ y=4 \ \ left { {{x=2} atop {y=4}} ight. [/latex] [latex]b). \ left { {{-2x+y=0/*3} atop {3x-3y=1}} ight. \ \ left { {{-6x+3y=0} atop {3x-3y=1}} ight. + \ ------- \ -3x=1/:(-3) \ x=- frac{1}{3} \ \ -2x+y=0 \ -2*(- frac{1}{3} )+y=0 \ frac{2}{3} +y=0 \ y=- frac{2}{3} \ \ left { {{x=- frac{1}{3} } atop {y=- frac{2}{3} }} ight. [/latex] [latex]c). \ left { {{3x-2y=-12/*5} atop {2x-5y=-19/*(-2)}} ight. \ \ left { {{15x-10y=-60} atop {-4x+10y=38}} ight. + \ -------- \ 11x=-22/:11 \ x=-2 \ \ 3x-2y=-12 \ 3*(-2)-2y=-12 \ -6-2y=-12 \ -2y=-12+6 \ -2y=-6/:(-2) \ y=3 \ \ left { {{x=-2} atop {y=3}} ight. [/latex] [latex]d). \ left { {{-4x+1,2y=-1/*5} atop {5x-6y=1,25}} ight. \ \ left { {{-20x+6y=-5} atop {5x-6y=1,25}} ight. + \ -------- \ -15x=-3,75/:(-15) \ x=0,25 \ \ -4x+1,2y=-1 \ -4*0,25+1,2y=-1 \ 1+1,2y=-1 \ 1,2y=-1+1 \ 1,2y=0/:1,2 \ y=0 \ \ left { {{x=0,25} atop {y=0}} ight. [/latex] [latex]e). \ left { {{3x+6(y-2)=0} atop {x+3y-4=0}} ight. \ \ left { {{3x+6y-12=0} atop {x+3y=4}} ight. \ \ left { {{3x+6y=12} atop {x+3y=4/*(-2)}} ight. \ \ left { {{3x+6y=12} atop {-2x-6y=-8}} ight. + \ -------- \ x=4 \ \ 3x+6y=12 \ 3*4+6y=12 \ 12+6y=12 \ 6y=12-12 \ 6y=0/:6 \ y=0 \ \ left { {{x=4} atop {y=0}} ight. [/latex]
