$\left \{ {{4x+2y=2} \atop {8x+3y=5}} \right.$ =>$\left \{ {{8x+4y=4} \atop {8x+3y=3}} \right.$ =>$\left \{ {{8x+4y=4} \atop {y=1}} \right.$ =>$\left \{ {{8x+4=4} \atop {y=1}} \right.$ =>$\left \{ {{8x=0} \atop {y=1}} \right.$ =>$\left \{ {{x=0} \atop {y=1}} \right.$ 

Vậy hpt có nghiệm(x;y) là (0:1)

b.$\left \{ {{3x+2y=6} \atop {x-y=2}} \right.$ =>$\left \{ {{3x+2y=6} \atop {2x-2y=4}} \right.$ =>$\left \{ {{3x+2y=6} \atop {5x=10}} \right.$ => $\left \{ {{3.2+2y=6} \atop {x=2}} \right.$ =>$\left \{ {{6+2y=6} \atop {x=2}} \right.$ =>$\left \{ {{2y=0} \atop {x=2}} \right.$ =>$\left \{ {{y=0} \atop {x=2}} \right.$ 

Vậy hpt có nghiệm (x;y) là (2;0)

c.$\left \{ {{x+2y=4} \atop {2x-3y=1}} \right.$ =>$\left \{ {{2x+4y=8} \atop {2x-3y=1}} \right.$ =>$\left \{ {{2x+4y=8} \atop {7y=7}} \right.$ =>$\left \{ {{2x+4.1=8} \atop {y=1}} \right.$ =>$\left \{ {{2x+4=8} \atop {y=1}} \right.$ =>$\left \{ {{2x=4} \atop {y=1}} \right.$ =>$\left \{ {{x=2} \atop {y=1}} \right.$ 

Vậy hpt có nghiệm (x;y) là (2;1)

B2

a.$\left \{ {{x+3y=7} \atop {2x-3y=0}} \right.$ =>$\left \{ {{x+3y=7} \atop {3x=7}} \right.$ =>$\left \{ {{3/7+3y=7} \atop {x=3/7}} \right.$ =>$\left \{ {{3y=46/7} \atop {x=3/7}} \right.$ =>$\left \{ {{y=46/21} \atop {x=3/7}} \right.$ 

 Vậy hpt có nghiệm (x;y) là (3/7;46/21)

b.$\left \{ {{x+2y=7} \atop {3x+2y=5}} \right.$ =>$\left \{ {{x+2y=7} \atop {-2x=2}} \right.$ => $\left \{ {{-1+2y=7} \atop {x=-1}} \right.$ =>$\left \{ {{2y=8} \atop {x=-1}} \right.$ =>$\left \{ {{y=4} \atop {x=-1}} \right.$ 

Vậy hpt có nghiệm (x;y) là (-1;4)