Question

$- 2 \sqrt{x + 5} + 10 = x$
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Answer 1

x=4
After squaring both sides, you get
4(x+5)=x^2-20x+100
Multiply
4x+20=x^2-20x+100
Collect like terms
4x+20-x^2+20x-100=0
Reorder
24x-80-x^2=0
Change signs & Write as difference. You end up with
x^2-4x-20x+80=0
Factor
x-4=0 , x-20=0
4=4 , 0=20
x=4