Question

9 класс, 30 баллов, очень-очень срочно! (если поможете решить правильно, скину еще несколько заданий с большими баллами)

Answer 1

X/(2x-9y) = -40 | 1/(2x-9) = -40/x
1/(2x-9y) + x = 3

-40/x + x = 3
x^2 - 3x - 40 = 0
(x - 8)(x + 5) = 0
x = 8 -> 1/(2x-9y) + 8 = 3, 1/(16-9y) = -5, 16-9y = -1/5, 9y = 16+1/5 = 16.2, y = 1.8 = 1 + 4/5
x = -5 -> 1/(-10-9y) - 5 = 3, 1(-10-9y) = 8, 9y+10 = -1/8, 9y = -10-1/8 = -10.125, y = -1.125 = -1 - 1/8

x1 = -5, y1 = -(1 + 1/8)
x2 = 8, y2 = 1 + 4/5

Answer 2

Сделаем замену
$\frac{1}{2x-9y}=m$
Тогда
$\left \{ {{m+x=3} \atop {m*x=-40}} \right.\\\\ \left \{ {{x=3-m} \atop {m(3-m)=- 40}} \right.\\\\ \left \{ {{x=3-m} \atop {3m-m ^{2}+40=0 }} \right.\\\\ \left \{ {{x=3-m} \atop { m^{2} -3m-40=0}} \right.\\\\ \left \{ {{m _{1} =8} \atop {x _{1} =-5}} \right. \left \{ {{m _{2}=-5 } \atop {x _{2} =8} \right. \\\\ \left \{ {{x=-5} \atop { \frac{1}{2x-9y} =8}} \right. \\\\ \left \{ {{x=-5} \atop {2x-9y= \frac{1}{8} }} \right.\\\\ \left \{ {{x=-5} \atop {9y=-10- \frac{1}{8} }} \right.$

$\left \{ {{x=-5} \atop {9y=-10 \frac{1}{8} }} \right. \left \{ {{x=-5} \atop {y=-1 \frac{1}{8} }} \right.\\\\ \left \{ {{x=8} \atop { \frac{1}{2x-9y}=-5 }} \right.\\\\ \left \{ {{x=8} \atop {2x-9y=- \frac{1}{5} }} \right.\\\\ \left \{ {{x=8} \atop {9y =16,2}} \right.\\\\ \left \{ {{x=8} \atop {y=1,8}} \right.$
Ответ: (-5 ; - 1 1/8) , ( 8 , 1,8)