Răspuns:
ultima cifră: a) 3; b) 5; c) 2
Explicație pas cu pas:
2019 = 4×504 + 3
2019 = 2×1009 + 1
2020 = 4×505
2021 = 4×505 + 1
2022 = 4×505 + 2
a) U(3²⁰¹⁹+5²⁰²⁰+1²⁰²¹) = U(U(3²⁰¹⁹) + U(5²⁰²⁰) + U(1²⁰²¹)) = U(U(3³) + U(5) + U(1)) = U(7+5+1) = U(13) = 3
b) U(2²⁰¹⁹+6²⁰²⁰+2019⁰) = U(U(2²⁰¹⁹) + U(6²⁰²⁰) + U(9⁰)) = U(U(2³) + U(6) + U(1)) = U(8+6+1) = U(15) = 5
c) U(4²⁰¹⁹+7²⁰²⁰+8²⁰²¹-9²⁰²²) = U(U(4²⁰¹⁹) + U(7²⁰²⁰) + U(8²⁰²¹) - U(9²⁰²²)) = U(U(4¹) + U(7⁴) + U(8¹) - U(9²)) = U(4 + 1 + 8 - 1) = U(12) = 2
