Đáp án:

 CHÚC BN HOK TỐT !!!

Giải thích các bước giải:

1) $\left \{ {{2x+y=3} \atop {3x-y=7}} \right.$ 

$\left \{ {{5x=10} \atop {2x+y=3}} \right.$

$\left \{ {{x=2} \atop {y=-1}} \right.$

2) $\left \{ {{2x+5y=7} \atop {2x-2y=0}} \right.$ 

$\left \{ {{7y=7} \atop {2x-2y=0}} \right.$

$\left \{ {{y=1} \atop {x=1}} \right.$

3) $\left \{ {{2x+3y=2} \atop {3x-2y=3}} \right.$ 

$\left \{ {{6x+9y=6} \atop {6x-4y=6}} \right.$

$\left \{ {{2x+3y=2} \atop {13y=0}} \right.$

$\left \{ {{y=0} \atop {x=1}} \right.$

4) $\left \{ {{x√2-2y=3} \atop {2x+y√2=-√2}} \right.$ 

$\left \{ {{2x-2√2y=3√2} \atop {2x+y√2=-√2}} \right.$

$\left \{ {{x√2-2y=3} \atop {3√2y=-4√2}} \right.$

$\left \{ {{x√2-2y=3} \atop {y=-4/3}} \right.$

$\left \{ {{y=-4/3} \atop {x=√2/6}} \right.$

8) Đặt $\frac{1}{x+2}$ = a , $\frac{1}{y+1}$ = b

-> $\left \{ {{a+b=2} \atop {3a-2b=1}} \right.$ 

$\left \{ {{3a+3b=6} \atop {3a-2b=1}} \right.$

$\left \{ {{5b=5} \atop {a+b=2}} \right.$

$\left \{ {{b=1} \atop {a=1}} \right.$

-> $\left \{ {{1/x+2=1} \atop {1/y+1=1}} \right.$ ĐK : x$\neq$ -2,y$\neq$ -1

$\left \{ {{x+2=1} \atop {y+1=1}} \right.$

$\left \{ {{y=0} \atop {x=-1}} \right.$

4) $\left \{ {{2x-y=-3} \atop {2x-y=2}} \right.$ 

$\left \{ {{2x-y=2} \atop {0x=-5}} \right.$

-> vô nghiệm

5) $\left \{ {{x+y=2} \atop {2x+y=2}} \right.$ 

$\left \{ {{y=2} \atop {x=0}} \right.$

6) $\left \{ {{2x-y=1} \atop {x+y=2}} \right.$ 

$\left \{ {{3x=3} \atop {x+y=2}} \right.$

$\left \{ {{y=1} \atop {x=1}} \right.$

7) $\left \{ {{x√2-y√3=1} \atop {x+y√3=√2}} \right.$ 

$\left \{ {{x√2-y√3=1} \atop {x√2+√6y=2}} \right.$

$\left \{ {{(√6+√3)y=1} \atop {x+y√3=√2}} \right.$

$\left \{ {{y=√6-√3/3} \atop {x=1}} \right.$

Chuyên mục giải những câu hỏi cũ :Đ

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