\(10^{34}=2^{34}.5^{34}=2^3.2^{31}.5^{34}=8.2^{31}.5^{34}⋮8\)
\(\Rightarrow b=10^{34}+8⋮8\) (1)
Lại có:
\(10\equiv1\left(\mod9\right)\Rightarrow10^{34}\equiv1\left(\mod9\right)\)
\(\Rightarrow10^{34}+8\equiv9\left(\mod9\right)\)
\(\Rightarrow10^{34}+8⋮9\) (2)
(1);(2) \(\Rightarrow10^{34}+8⋮72\) (đpcm)