Question

Care este ultima cifra a 2³¹+3⁴² = ??? Plsssss !!!

Answer 1

U(2^31)
U(2^1)=2
U(2^2)=4
U(2^3)=8
U(2^4)=6
U(2^5)=2
=> puterile lui 2 (2,4,8,6) se repeta din 4 in 4
=> 31:4=7 rest 3
=> U(2^31)=8


U(3^42)
U(3^1)=3
U(3^2)=9
U(3^3)=7
U(3^4)=1
U(3^5)=3
=> puterile lui 3 (3,9,7,1) se repeta din 4 in 4
=> 42:4=10 rest 2
=> U(3^42)=9
=> U(2^31+3^42)=U(8+9)=U(17)=7

Answer 2

31:4 = 7 (rest 3) => u(2³¹) = u(⁴ˣ⁷⁺³) = 8 ;

42:4 = 10 (rest 2) => u(3⁴²) = u(⁴ˣ¹⁰⁺²) = 9 ;