Find all values of x such that sqrt(4x^2) - sqrt(x^2) = 16.
sqrt (4x^2) - sqrt (x^2) = 16
sqrt (4) * sqrt (x^2) - sqrt (x^2) = 16
2 sqrt (x^2) - sqrt (x^2) = 16
sqrt (x^2) = 16 square both sides
x^2 = 256 take both roots
x = 16 or x = -16
