Question

One of the roots of quadratic equation \[2 x^2 + kx - 2 = 0\] is –2. find k.

Answer 1

\[2 x^2 + kx - 2 = 0\] 

One of the roots is –2 so, it will satisfy the given equation.  

\[2 \left( - 2 \right)^2 + k\left( - 2 \right) - 2 = 0\]
\[ \Rightarrow 8 - 2k - 2 = 0\]
\[ \Rightarrow 6 - 2k = 0\]
\[ \Rightarrow 6 = 2k\]
\[ \Rightarrow k = 3\]