Math Gold Medalist

Lor

2019 AMC 8 

Problem 20

How many different real numbers $x$ satisfy the equation\[(x^{2}-5)^{2}=16?\]

$\textbf{(A) }0\qquad\textbf{(B) }1\qquad\textbf{(C) }2\qquad\textbf{(D) }4\qquad\textbf{(E) }8$

nth root

x^2-5=+16 or -16

x^2=21 or -11

x=+-sqrt(21)

2019 AMC 8 Problem 20

   Solution