Question

1. Write a proof for the biconditional using the inverse and contrapositive.
x ≥ 4 if and only if 3x ≥ 12.

2. Write a proof for the statement.
If a quadrilateral is a square, then the quadrilateral is a rectangle

Please need help

Answer 1

\[x\geq 4\implies 3\times x\geq 3\times 4\] is one direction

Answer 2

\[3x\geq 12\implies \frac{3x}{3}\geq \frac{12}{3}\] goes the other way