A value of $b$ for which the equations $$\begin{aligned}
& x ^ { 2 } + b x - 1 = 0 \\
& x ^ { 2 } + x + b = 0
\end{aligned}$$ have one root in common is (A) $- \sqrt { 2 }$ (B) $- i \sqrt { 3 }$ (C) $i \sqrt { 5 }$ (D) $\sqrt { 2 }$
A value of $b$ for which the equations
$$\begin{aligned}
& x ^ { 2 } + b x - 1 = 0 \\
& x ^ { 2 } + x + b = 0
\end{aligned}$$
have one root in common is\\
(A) $- \sqrt { 2 }$\\
(B) $- i \sqrt { 3 }$\\
(C) $i \sqrt { 5 }$\\
(D) $\sqrt { 2 }$