Question

Даю 25 Баллов помогитеее

Answer 1

Ответ:

$(-1; \quad 4); \quad (2; \quad -1); \quad (\frac{2}{3}; \quad 1);$

Объяснение:

$a) \quad \left \{ {{2x+3y=10} \atop {x=2y-9}} \right. \Leftrightarrow \left \{ {{2(2y-9)+3y=10} \atop {x=2y-9}} \right. \Leftrightarrow \left \{ {{4y-18+3y=10} \atop {x=2y-9}} \right. \Leftrightarrow \left \{ {{(4+3)y=10+18} \atop {x=2y-9}} \right. \Leftrightarrow$

$\Leftrightarrow \left \{ {{7y=28} \atop {x=2y-9}} \right. \Leftrightarrow \left \{ {{y=4} \atop {x=2y-9}} \right. \Leftrightarrow \left \{ {{y=4} \atop {x=2 \cdot 4-9}} \right. \Leftrightarrow \left \{ {{x=-1} \atop {y=4}} \right. ;$

$(-1; \quad 4);$

$b) \quad \left \{ {{x-y=3} \atop {3x+4y=2}} \right. \Leftrightarrow \left \{ {{x=y+3} \atop {3x+4y=2}} \right. \Leftrightarrow \left \{ {{x=y+3} \atop {3(y+3)+4y=2}} \right. \Leftrightarrow \left \{ {{x=y+3} \atop {3y+9+4y=2}} \right. \Leftrightarrow \left \{ {{x=y+3} \atop {(3+4)y=2-9}} \right. \Leftrightarrow$

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

$(2; \quad -1);$

$c) \quad \left \{ {{3x-y=1} \atop {3x-2y=0}} \right. \Leftrightarrow \left \{ {{3x=y+1} \atop {3x-2y=0}} \right. \Leftrightarrow \left \{ {{3x=y+1} \atop {y+1-2y=0}} \right. \Leftrightarrow \left \{ {{3x=y+1} \atop {(1-2)y=-1}} \right. \Leftrightarrow \left \{ {{3x=y+1} \atop {-y=-1}} \right. \Leftrightarrow$

$\Leftrightarrow \left \{ {{3x=y+1} \atop {y=1}} \right. \Leftrightarrow \left \{ {{3x=1+1} \atop {y=1}} \right. \Leftrightarrow \left \{ {{3x=2} \atop {y=1}} \right. \Leftrightarrow \left \{ {{x=\frac{2}{3}} \atop {y=1}} \right. ;$

$(\frac{2}{3}; \quad 1);$