axe211 3sin^2x+sinxcosx - 2cosx = 0

делим на cos^2 x

3tg^x +tgx -2 = 0
замена
tgx = t
3t^2 +t - 2 =0
d= 1 - 4 *3*(-2) =  25

x1 = -1 + 5/ 6 = 4/6

x2 = -1 -5 / 6 = -1

tg x = 4/6                tgx = -1

x = arctg 4/6 + pk, k e z;

x = p + pn, n e z;

ответ : x = arctg 4/6 + pk, k e z;  x = p + pn, n e z.