Question

ДАЮ 45 БАЛОВ
розкажіть систему рівнянь
{2(x-y)+9=0
{8x-25y-15-0​

Answer 1

$\displaystyle\bf\\\left \{ {{2(x - y) + 9 = 0} \atop {8x - 25y - 15 = 0 }} \right. \\ \displaystyle\bf\\\left \{ {{2x - 2y = - 9 \: \: | \times ( - 4) } \atop {8x - 25y = 15 }} \right. \\ \displaystyle\bf\\ + \left \{ {{ - 8x + 8y = 36} \atop {8x - 25y = 15 }} \right. \\ \\ 8y - 25y = 36 + 15 \\ - 17y = 51 \\ y = 51 \div ( - 17) \\ y = - 3 \\ \\ 2x - 2 \times ( - 3) = - 9 \\ 2x + 6 = - 9 \\ 2x = - 9 - 6 \\ 2x = - 15 \\ x = - 15 \div 2 \\ x = - 7.5$

Ответ: ( - 7,5 ; - 3 )