Question 14
Find the last digit of $2+2^2+2^3+\cdots+2^{2020}+2^{2021}$.
HKIMO 2026 THPT (Grades 10–12 shared) National Preliminary Set 03 Question 14
HKIMO · HKIMO 2026 THPT (Grades 10–12 shared) National Preliminary Set 03
HKIMO · HKIMO 2026 THPT (Grades 10–12 shared) National Preliminary Set 03