Объяснение:

[tex] |x| - 4x = 9 \\ x - 4x = 9.x \geqslant 0 \\ - x - 4x = 9.x < 0 \\ x = - 3 .x \geqslant 0 \\ x = - \frac{9}{5}.x < 0 \\ [/tex]

Порожня множина

[tex]x = - \frac{9}{5} = - 1 \frac{4}{5} [/tex]