1
GATE AI 2025
MCQ (Single Correct Answer)
+2
-0

Let $A \in \mathbb{R}^{n \times n}$ be such that $A^3=A$. Which one of the following statements is ALWAYS correct?

A
$A$ is invertible
B
Determinant of $A$ is 0
C
The sum of the diagonal elements of $A$ is 1
D
A and $A^2$ have the same rank
2
GATE AI 2025
MCQ (More than One Correct Answer)
+2
-0

An $n \times n$ matrix $A$ with real entries satisfies the property: $\|A x\|^2=\|x\|^2$ for all $x \in R^n$ where $\|\cdot\|$ denotes the Euclidean norm. Which of the following statements is/are ALWAYS correct?

A
$A$ must be orthogonal
B
$A=I$, where $I$ denotes the identity matrix, is the only solution
C
The eigenvalues of $A$ are either +1 or $-1$
D
A has full rank