Attempt the question, check the explanation, and continue with similar questions to build confidence before exams.
√(x2 - x1 + y2 - y1 + z2 - z1)
√((x2 - x1)² + (y2 - y1)² + (z2 - z1)²)
√(|x2 - x1| + |y2 - y1| + |z2 - z1|)
x2 - x1 + y2 - y1 + z2 - z1
Continue with nearby questions to strengthen the same chapter concept while you still have the context fresh in mind.