Answer
No solution
Work Step by Step
$$\begin{array}{rl}
k^2-10 k+ 40 & =5 \\
k^2-10 k & =5-40 \\
k^2-10 k & =-35 \\
k^2-10 k+\left(\frac{10}{2}\right)^2 & =-35+\left(\frac{10}{2}\right)^2 \\
k^2-10 k+5^2 & =-35+5^2 \\
(k-5)^2 & = -10
\end{array}$$ There is no solution to the equation. We cannot take the square root of a negative number.
