How do I solve this and check all the solutions?

Answer:
x = 2
Step-by-step explanation:
(Square both sides)
20 - 8x = x^2
(Solve 20 - 8x = x^2)
x = 2 , x = 10
x = 10 is false, so the answer is x = 2.
Answer:
x=2
Step-by-step explanation:
√20-8x=x
2√5-2x=x (by simplfing redical expression)
4(5-2x)=x^2 (square both side)
20-8x=x^2
20-8x-x^2=0
-x^2-8x+20=0
x^2+8x-20=0
x=2
Note:There is a another answer x=-10 But it's wouldn't fit out with this equation