2a - 1 = [6 ^ 1/2] . [(a² + 5) ^ 1/2] . cos(60)
2a - 1 = V(6) . V(a² + 5) . [1/2]
2a - 1 = V6(a² + 5)
2
2(2a-1) =V6(a² + 5)
(4a-2)^2 = (V6a² + 30)^2
[16a² - 16a + 4] = 6a² + 30
16a² - 16a + 4 - 6a² - 30 = 0
10a² - 16a - 26 = 0 (;2)
5a² -8a - 13 = 0
delta= (-8)^2 -4.5.(-13) = 64+ 260= 324
X =8+/-v324 ==> x = 8 +/- 18
2.5 10
x1 = 8 + 10 ==> x1 = 18
10 10
x2= 8 - 10 ==> x2 = - 2
10 10