Vì g(a+b)=g(a.b) nên ta có :
+)g(2021)=g(2020+1)=g(2020.1)=g(2020)
⇒g(2021)=g(2020)
+)g(2020)=g(2019+1)=g(2019.1)=g(2019)
⇒g(2020)=g(2019)
...
+) g(2) = g(1 + 1) = g(1. 1) = g(1)
=> g(2) = g(1)
=> g(2021) = g(2020) = ... = g(1) mà g(1) = 2020
=> g(2021) = 2020
Xin hay nhất