Решите способом выделения полного квадрата

-x+3x^2-70=0

3x^2 - x - 70 = 0

(sqrt (3) x - (1/sqrt (3))) ^2 - 70 (1/3) = 0

(sqrt (3) x - (1/sqrt (3))) ^2 = 70 (1/3)

sqrt (3) x - (1/sqrt (3)) = sqrt (211) / sqrt (3)

sqrt (3) x = (1/sqrt (3)) + sqrt (211) / sqrt (3)

x = (sqrt (211) + 1) / 3