import math

A = [3, 4]
B = [1, 2]

# 1. A + B
add_result = [a + b for a, b in zip(A, B)]
print("A + B =", add_result)

# 2. 2 × A
scalar_result = [2 * a for a in A]
print("2 × A =", scalar_result)

# 3. A的长度
norm = math.sqrt(sum(a**2 for a in A))
print("A的长度 =", norm)