99999999995=19999999999x5
=>\(\frac{\text{19999999999}}{99999999995}=\frac{\text{19999999999}}{\text{19999999999.5}}=\frac{1}{5}\)
Đặt A=\(\frac{19999999999}{99999999995}\)
Xét tử số: 19999999999=2000000000-1=2.1010-1
Xét mẫu số: 99999999995=100000000000-5=10.1010-5=5(2.1010-1)
Suy ra A=\(\frac{2.10^{10}-1}{\text{ }5\left(2.10^{10}-1\right)}\)=\(\frac{1}{5}\)