Question

TÍNH \(E=\frac{1.98+2.97+...+98.1}{1.2+2.3+...+98.99}\)

Answer 1

đặt \(B=1.2+2.3+...+98.99\)

đặt \(A=1.98+2.97+...+98.1\)

\(=1+\left(1+2\right)+...+\left(1+2+...+98\right)=\frac{1.2}{2}+\frac{2.3}{2}+...+\frac{98.99}{2}\)

\(=\frac{1.2+2.3+...+98.99}{2}=\frac{B}{2}\)

\(\Rightarrow E=\frac{\frac{B}{2}}{B}=\frac{1}{2}\)