Answer
See explanations.
Work Step by Step
Method 1. Let $u=\sqrt x$, we have $u^2-5u+4=0$ and $(u-1)(u-1)=0$ which gives $u=1,4$, thus $x=1, 16$
Method 2. Rewrite the equation as $5\sqrt x=x+4$, take square on both side to get $25x=x^2+8x+16$ or $x^2-17x+16=0$ which gives $(x-1)(x-16)=0$ and $x=1, 16$
