Tính nhanh
b, A=\(\dfrac{7}{8}+\dfrac{7}{24}+\dfrac{7}{48}+...+\dfrac{7}{10200}\)
A=\(\dfrac{7}{2.4}+\dfrac{7}{4.6}+...+\dfrac{7}{100.102}\)
A=\(2.\left(\dfrac{7}{2.4}+\dfrac{7}{4.6}+...+\dfrac{7}{100.102}\right)\)
A=\(\dfrac{7}{2}.\left(\dfrac{1}{2.4}+\dfrac{1}{4.6}+...+\dfrac{1}{100.102}\right)\)
A=\(\dfrac{7}{2}.\left(\dfrac{1}{2}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{6}+...+\dfrac{1}{100}-\dfrac{1}{102}\right)\)
A=\(\dfrac{7}{2}.\left(\dfrac{1}{2}-\dfrac{1}{102}\right)\)
A=\(\dfrac{7}{2}.\dfrac{50}{102}\)
A=\(\dfrac{175}{102}\)
Đúng 0
Bình luận (0)
.
