Find $k$ such that $2x^2 + 5x + k = 0$ has equal roots Anyone have a method for solving this?

The equation $2x^2 + 5x + k = 0$ has equal roots. Find the value of $k$.


One method goes like this:
Two equal roots means, that you can write $2x^2+5x+k=a(x-b)^2$ where $b$ is the root.
Multiply this out and compare the coefficients.
