a, \(7^{2019}=7^3.7^{2016}=343.\left(7^4\right)^{504}=343.\left(...1\right)^{504}=343.\left(...1\right)=\left(....3\right)\)
b, \(12^{2019}=12^3.12^{2016}=\left(...8\right).\left(12^4\right)^{504}=\left(...8\right).\left(...6\right)^{504}=\left(...8\right).\left(...6\right)=\left(...8\right)\)
c, \(11^8+12^8+13^8+14^8+15^8+16^8\)
\(=\left(...1\right)+\left(12^4\right)^2+\left(13^4\right)^2+\left(...5\right)+\left(...6\right)=\left(....1\right)+\left(....6\right)^2+\left(...1\right)^2+\left(...5\right)+\left(...6\right)\)
\(=\left(....1\right)+\left(....6\right)+\left(...1\right)+\left(...5\right)+\left(...6\right)=\left(...9\right)\)
d, \(11^{123}+13^{124}+15^{125}=\left(....1\right)+\left(13^4\right)^{31}+\left(....5\right)=\left(...1\right)+\left(...1\right)+\left(....5\right)=\left(...7\right)\)
\(a,7^{2019}=\left[7^3\right]^{673}=\overline{....}3^{673}=\overline{....3}\)
Vậy chữ số tận cùng của 72019 là 3
\(b,12^{2019}=\left[12^3\right]^{673}=\overline{....8}^{673}=\overline{....8}\)
Vậy chữ số tận cùng của 122019 là 8
Làm nốt
