\(=\dfrac{1}{3}-\dfrac{1}{2}\left(\dfrac{2}{3\cdot5}+\dfrac{2}{5\cdot7}+...+\dfrac{2}{33\cdot35}\right)\)
\(=\dfrac{1}{3}-\dfrac{1}{2}\cdot\left(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{33}-\dfrac{1}{35}\right)\)
\(=\dfrac{1}{3}-\dfrac{1}{2}\cdot\dfrac{32}{105}=\dfrac{19}{105}\)
Tính nhanh : a/ A= 1/1.2 +1/2.3+....+1/49.50 và câu b/ B = -1/3-1/15-....-1/33.35
A= 33. 102+672-33.35
B=36 .15 .2+8.41.9+6.44.12
tính nhanh mình tích cho
tính tỉ số \(\frac{M}{N}\) biết M = \(\frac{-40}{31.39}+\frac{-35}{39.46}+\frac{-30}{46.52}+\frac{-25}{52.57}\)
N = \(\frac{1}{31.33}+\frac{1}{33.35}+\frac{1}{35.37}+...+\frac{1}{55.57}\)
tinh gia tri bieu thuc lop 6 : 6/5.7+6/7.9+6/9.11+......+6/33.35
Tính giá trị biểu thức:
6/5.7+6/7.9+6/9.11+......+6/33.35
2/5.7+2/7.9+2/9.11+.....+2/31.33+2/33.35
giúp minh cái này voi cac ban minh se tick cho cac ban tra loi dung
chứng minh
a) (a+a^2+a^3+a^4+................+a^29+a^30) chia hết (a+1)
b)15/460+15/498+15/754+.............+15/6160<1
c)1/2-1/4+1/8-1/16++1/32-1/64<1/3
d)1/3-2/3^2+3/3^3-4/3^4+...........+99/3^99+100/3^100
giúp mk vs nha
3/5:(-1/15-1/6)+3/5:( -1/2-1 16/15) = ?
3/3:(-1/15-1/6)+3/5:(-1/2-16/15)
