# Math Help - Quadritic residues and more

1. ## Quadritic residues and more

(a) Determine Q240.
(b) Determine T(U240).
(c) Find all solutions of x^2(is congruent to) -23 (mod 240).

I was able to figure out part (a), but I don't know what to do for part (b) and (c). I believe my solution for (a) was {1,49,119,199}

For (a) and (b), the 240 is subscript of course.

$x^2 \equiv 9(\bmod 2^4)$
$x^2\equiv 1(\bmod 3)$
$x^2 \equiv 2(\bmod 5)$.