(х-3)(х во 2-ой ступени +3х+9)-х(х-5)(х+5)=48

(х - 3) (х + 3х + 9) - х (х - 5) (х + 5) = 48.

x * x + 3x * x + 9 * x - 3 * x - 3 * 3x - 3 * 9 - x (x - 25) = 48.

x + 3x + 9x - 3x - 9x - 27 - x + 25x = 48.

x (1 - 1) + x (3 - 3) + x (9 - 9 + 25) - 27 = 48.

0 + 0 + 25x = 48 + 27.

25x = 75.

x = 75 : 25 = 3,

Ответ: х = 3.