Answer:
distance formula; definition of congruence ; if two consecutive sides of a rectangle are congruent, then it's a square
Step-by-step explanation:
Given that RSTU is a rectangle with vertices;

So, using the distance formula;

Reason; distance formula

Since both side RS and ST have the same length, then;

Reason: definition of congruence
So, since two consecutive sides of a rectangle are congruent then;

Reason: if two consecutive sides of a rectangle are congruent, then it's a square