# Value of 'a' for which $x^2-(a+2)x+2a$ is perfect square is :

$\begin{array}{1 1}(A)\;0&(B)\;1\\(C)\;2&(D)\;3\end{array}$

For perfect square,
D=0
$\Rightarrow (a+2)^2-4(2a)=0$
$\Rightarrow a^2+4a+4-8a=0$
$\Rightarrow a^2-4a+4=0$
$\Rightarrow (a-2)^2=0$
$\Rightarrow a=2$
Hence (C) is the correct answer.