$(3x - 2)(3x + 2) + (4x - 5)^2 = 10x + 21$
$9x^2 - 4 + 16x^2 - 40x + 25 - 10x - 21 = 0$
$25x^2 - 50x = 0$
25x(x − 2) = 0
25x = 0
x = 0
или
x − 2 = 0
x = 2
Ответ: x = 0 или x = 2

$(2x - 1)(x + 8) - (x - 1)(x + 1) = 15x$
$2x^2 - x + 16x - 8 - (x^2 - 1) - 15x = 0$
$2x^2 + 15x - 8 - x^2 + 1 - 15x = 0$
$x^2 - 7 = 0$
$x^2 = 7$
$x = \sqrt{7}$
или
$x = -\sqrt{7}$
Ответ: $x = -\sqrt{7}$ и $x = \sqrt{7}$