Question

fie a=9^2020-7^2020 ultima cifra a numarului a este

Answer 1

$\large{\underbrace{\underline{\bf{Întrebare}}}}:$

• Aflați ultima cifră a numărului a.

$\large{\underbrace{\underline{\bf{Datele}}}}:$

• $a = {9}^{2020} - {7}^{2020}$

$\large{\underbrace{\underline{\bf{Rezolvare}}}}:$

${9}^{2020} = ....?$

${9}^{1} = ......9$

${9}^{2} = .........1$

${9}^{3} = ..........9$

${9}^{4} = ..........1$

2020 ÷ 2 = 1010 rest 0

$\color{blue}{9}^{2020} = .......1$

$\space$

${7}^{2020} = .....?$

${7}^{1} = .....7$

${7}^{2} = .....9$

${7}^{3} = ......3$

${7}^{4} = .......1$

${7}^{5} = ........7$

etc.....

2020 ÷ 4 = 505 rest 0

$\color{blue}{7}^{2020} = .......1$

1 - 1 = 0

$\color{red}\boxed{\boxed{{9}^{2020} - {7}^{2020} = ........0}}$