Tính nhanh:
E=1/99-1/99.98-1/97.96-.......-1/3.2-1/2.1
Những câu hỏi liên quan
Tính nhanh 1/99 - 1/99.98 - 1/98.97 - 1/97.96 - ... - 1/3.2 -1/2.1
tính hợp lí 1/99 - 1/99.98 - 1/98.97 - 1/ 97.96 - ... -1/3.2 - 1/2.1
\(\frac{1}{99}-\frac{1}{99.98}-\frac{1}{98.97}-\frac{1}{97.96}+......+\frac{1}{2.1}\)
= \(\frac{1}{99}-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{98.99}\right)\)
= \(\frac{1}{99}-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{98}-\frac{1}{99}\right)\)
= \(\frac{1}{99}-\left(1-\frac{1}{99}\right)\)
= \(\frac{1}{99}-\frac{98}{99}\)
= \(\frac{-97}{99}\)
Đúng 2
Bình luận (0)
1/99 - 1/99.98 - 1/98.97 - 1/97.96 -...-1/3.2 -1/2.1
Giải:
\(\dfrac{1}{99}-\dfrac{1}{99.98}-\dfrac{1}{98.97}-\dfrac{1}{97.96}-...-\dfrac{1}{3.2}-\dfrac{1}{2.1}\)
\(=-\left(-\dfrac{1}{99}+\dfrac{1}{99.98}+\dfrac{1}{98.97}+\dfrac{1}{97.96}+...+\dfrac{1}{3.2}+\dfrac{1}{2.1}\right)\)
\(=-\left(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}+...+\dfrac{1}{97.98}+\dfrac{1}{98.99}-\dfrac{1}{99}\right)\)
\(=-\left(\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+...+\dfrac{1}{97}-\dfrac{1}{98}+\dfrac{1}{98}-\dfrac{1}{99}-\dfrac{1}{99}\right)\)
\(=-\left(\dfrac{1}{1}-\dfrac{1}{99}-\dfrac{1}{99}\right)\)
\(=-\dfrac{97}{99}\)
Vậy ...
Đúng 0
Bình luận (1)
Tính nhanh :
1/99 - 1/99.98 - 1/98.97 - 1/97.96 - ... - 1/3.2 - 1/2.1
Giúp mik vs
\(\frac{1}{99}-\frac{1}{99.98}-\frac{1}{98.97}-\frac{1}{97.96}-...-\frac{1}{3.2}-\frac{1}{2.1}\)
\(=\frac{1}{99}-\left(\frac{1}{99.98}+\frac{1}{98.97}+\frac{1}{97.96}+...+\frac{1}{3.2}+\frac{1}{2.1}\right)\)
\(=\frac{1}{99}-\left(\frac{1}{99}-\frac{1}{98}+\frac{1}{98}-\frac{1}{97}+\frac{1}{97}-\frac{1}{96}+...+\frac{1}{3}-\frac{1}{2}+\frac{1}{2}-\frac{1}{1}\right)\)
\(=\frac{1}{99}-\left(\frac{1}{99}-1\right)=\frac{1}{99}-\frac{1}{99}+1=1\)
Đúng 21
Bình luận (0)
Xem thêm câu trả lời
Giúp mik với : 1/99 - 1/99.98 - 1/98.97 - 1/97.96 - ...- 1/3.2 - 1/2.1
\(\dfrac{-1}{99}\dfrac{1}{99.98}-\dfrac{1}{98.97}-\dfrac{1}{97.96}-...\dfrac{1}{3.2}-\dfrac{1}{2.1}\)
=-1/99-(1-1/2+1/2-1/3+...+1/98-1/99)
=-2/99+1=97/99
Đúng 0
Bình luận (0)
1/99 - 1/99.98 - 1/98.97 - 1/97.96 - 1/96.95 - ... - 1/3.2 - 1/2.1
tính giùm mình nha các bạn
\(\frac{1}{99}-\frac{1}{99.98}-\frac{1}{98.97}-...-\frac{1}{3.2}-\frac{1}{2.1}\)
\(=\frac{1}{99}-\left(\frac{1}{1.2}+\frac{1}{2.3}+...+\frac{1}{97.98}+\frac{1}{98.99}\right)\)
\(=\frac{1}{99}-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{98}-\frac{1}{99}\right)\)
\(=\frac{1}{99}-\left(1-\frac{1}{99}\right)\)
\(=\frac{1}{99}-\frac{98}{99}\)
\(=-\frac{97}{99}\)
Ủng hộ !
Đúng 0
Bình luận (0)
tính nhanh
\(\frac{1}{99}-\frac{1}{99.98}-\frac{1}{98.97}-\frac{1}{97.96}-...-\frac{1}{3.2}-\frac{1}{2.1}\)
\(=\frac{1}{99}-\left(\frac{1}{99.98}+\frac{1}{98.97}+...+\frac{1}{3.2}+\frac{1}{2.1}\right)\)
\(=\frac{1}{99}-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{98}-\frac{1}{99}\right)\)
\(=\frac{1}{99}-\frac{98}{99}=-\frac{97}{99}\)
Đúng 0
Bình luận (0)
\(\frac{1}{99}-\frac{1}{99.98}-\frac{1}{98.97}-\frac{1}{97.96}-...-\frac{1}{3.2}-\frac{1}{2.1}\)
\(\frac{1}{99}-\frac{1}{99.98}-\frac{1}{98.97}-...-\frac{1}{3.2}-\frac{1}{2.1}\)
\(=\frac{1}{99}-\frac{1}{99}+\frac{1}{98}-\frac{1}{98}+\frac{1}{97}-....-\frac{1}{3}+\frac{1}{2}-\frac{1}{2}+1\)
\(\frac{1}{99}+1=\frac{100}{99}\)
\(\frac{1}{99}-\frac{1}{99.98}-\frac{1}{98.97}-\frac{1}{97.96}-...-\frac{1}{3.2}-\frac{1}{2.1}\)
\(=-\left(\frac{1}{99}+\frac{1}{99.98}+\frac{1}{98.97}+\frac{1}{97.96}+...+\frac{1}{3.2}+\frac{1}{2.1}\right)\)
\(=-\left(\frac{1}{99}-\frac{1}{98}+\frac{1}{98}-\frac{1}{97}+\frac{1}{97}-\frac{1}{96}+...+\frac{1}{3}-\frac{1}{2}+\frac{1}{2}-1\right)\)
\(=-\left(\frac{1}{99}-1\right)\)
\(=-\frac{98}{99}\)
cho mk sửa dòng thứ hai:
\(=\frac{1}{99}-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{96}-\frac{1}{97}+\frac{1}{97}-\frac{1}{98}+\frac{1}{98}-\frac{1}{99}\right)\)
Từ đó bn làm tiếp nha
sorry mn