Attempt the question, check the explanation, and continue with similar questions to build confidence before exams.
(x - 0)² + (y - 0)² = r²
(x + 0)² + (y + 0)² = r²
(x² + y² = r)
(x + y)² = r²
Continue with nearby questions to strengthen the same chapter concept while you still have the context fresh in mind.