Question

Evaluate

Answer 1

My textbook has got a different answer

So I did

Let x be this quantity

so We get
\[\huge x=\sqrt{20+x}\]
\[\huge 20+x =x ^{2}\]
\[\huge x ^{2} - x -20 =0\]
\[\huge (x-4)(x+5)=0\]
We get x=4 or x=-5
So discarding x=-5
x=4 is the answer i got
So is what i have done correct. Or i have made a foolish careless mistake