Question

решите систему уравнение 8х+2у=7
4х-у=9

Answer 1

$\left \{ {{-y=9 - 4x} \atop {8x + 2y = 7}} \right.$

$\left \{ {{y=4x - 9} \atop {8x + 2(4x-9) = 7}} \right.$

$\left \{ {{y=4x - 9} \atop {8x+8x-18 = 7}} \right.$

$\left \{ {{y=4x - 9} \atop {16x = 7 + 18}} \right.$

$\left \{ {{y=4x - 9} \atop {16 x = 25}} \right.$

$\left \{ {{y=4*1 \frac{9}{16} - 9} \atop {x=1 \frac{9}{16} }} \right.$

$\left \{ {{y=-2,75} \atop {x=1 \frac{9}{16} }} \right.$

Проверка:

$4 * ( \frac{25}{16} ) + 2,75 = 9$

$8 * \frac{25}{16} + 2*(-2,75) = 7$