Given 21x2 + 9x + 1 = 0
Recall that the roots of quadratic equation ax2 + bx + c = 0, where a ≠ 0, are given by
We have i2 = –1
By substituting –1 = i2 in the above equation, we get
Thus, the roots of the given equation are -\(\frac{3}{14}±\frac{\sqrt{3}}{42}\) i.