Answer:
x = 9, - 10
Step-by-step explanation:
[tex](90 - x)^ {\frac{1}{2}} = x \\\\Squaring \ both \ sides \\\\(( 90 - x)^{ \frac{1}{2}})^{2} = x^2\\\\90 -x = x^2\\\\x^2 + x - 90= 0\\\\x^2 + 10x - 9x - 90 = 0\\\\x(x + 10) - 9 (x + 10) = 0\\\\(x - 9)(x + 10) = 0\\\\x = 9 , \ x = \ - 10[/tex]
