1.Tính
\(\left(1-\dfrac{1^2}{100}\right)\left(1-\dfrac{2^2}{100}\right)\left(1-\dfrac{3^2}{100}\right)...\left(1-\dfrac{2018^2}{100}\right)\)
2.S=\(\dfrac{1}{4}+\dfrac{2}{4^2}+\dfrac{3}{4^3}+...+\dfrac{2017}{4^{2017}}\)
Chứng minh rằng S <\(\dfrac{1}{2}\)