Question

Tìm chữ số tận cùng của các số sau:

a) 12²⁰¹⁷; 23⁶⁹; 64⁷⁵; 98¹⁰⁵

b) 3²⁰¹⁷.7²⁰¹⁸.8²⁰¹⁹

Answer 1

Tự làm đi bạn ơi

Answer 2

\(a,12^{2017}=\left(12^4\right)^{504}.12=\left(...6\right)^{504}.12=\left(...2\right)\)

\(23^{69}=\left(23^4\right)^{17}.23=\left(...1\right)^{17}.23=\left(...3\right)\)

\(64^{75}=\left(64^2\right)^{37}.64=\left(...6\right)^{37}.64=\left(...4\right)\)

\(98^{105}=\left(98^4\right)^{26}.98=\left(...6\right)^{26}.98=\left(...8\right)\)

\(b,3^{2017}.7^{2018}.8^{2019}=\left(3^4\right)^{504}.3.\left(7^4\right)^{504}.7^2.\left(8^4\right)^{504}.8^3\)

\(=\left(...1\right).3.\left(...1\right).49.\left(...6\right).512\)

\(=\left(...3\right).\left(...9\right)\left(...2\right)=\left(...4\right)\)