-8² + 20х = 0,

20х = 64,

х = 3,2,

3х² - 2х - 16 = 0,

Д = (-2)² - 4*3*(-16) = 4 + 192 = 196,

х1 = (2 + 14) / 2*3 = 16/6 = 8/3 = 2 2/3,

х2 = (2 - 14) / 2*3 = -12/6 = -2,

4х² - 1/169 = 0,

4х² = 1/169,

х² = 1/169 : 4,

х² = 1/169 * 1/4,

х = ±√(1/169*1/4),

х = ± (1/13*1/2),

х = ± 1/26