\(f\left(x\right)=\dfrac{2^{x+1}}{10^x}-\dfrac{5^{x-1}}{10^x}=\dfrac{2}{5^x}-\dfrac{1}{5.2^x}=2.5^{-x}-\dfrac{1}{5}.2^{-x}\)
\(\Rightarrow\int f\left(x\right)dx=\int\left(2.5^{-x}-\dfrac{1}{5}.2^{-x}\right)dx=\int\left(-2.5^{-x}+\dfrac{1}{5}.2^{-x}\right)d\left(-x\right)\)
\(=\dfrac{-2.5^{-x}}{ln5}+\dfrac{2^{-x}}{5.ln2}+C=\dfrac{1}{2^x.5ln2}-\dfrac{2}{5^x.ln5}+C\)