Tìm A :
1 / A = ( 1 -\(\frac{1}{3}\)) + ( 1 - \(\frac{1}{15}\)) + ( 1 - \(\frac{1}{35}\)) + ( 1 - \(\frac{1}{63}\))
2 / A = ( 1 -\(\frac{1}{10}\)) + ( 1 - \(\frac{1}{40}\)) + ( 1 - \(\frac{1}{88}\)) + ( 1 - \(\frac{1}{154}\))
3 / A = \(\frac{2}{3}+\frac{14}{15}+\frac{34}{35}+....+\frac{9998}{9999}\)
4 / A = \(\frac{9}{10}+\frac{39}{40}+\frac{87}{88}+...+\frac{1119}{1120}\)
5 / A = \(\frac{9}{10}+\frac{39}{40}+\frac{87}{88}+\frac{153}{154}\)
Trình bày cách làm hộ mình nha ! Cảm ơn rất nhiều !
bạn ơi tách ra thừa số chung rồi làm như bình thường nha
1, A=\(\left(1+1+1+1\right)\)-\(\left(\frac{1}{3}+\frac{1}{15}+\frac{1}{35}+\frac{1}{63}\right)\)
=4-\(\left(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}\right)\)
= 4-\(\left(\frac{1}{1}-\frac{1}{3}+...+\frac{1}{7}-\frac{1}{9}\right)\)
=4-\(\left(1-\frac{1}{9}\right)\)
= 4-\(\frac{8}{9}\)
= \(\frac{7}{9}\)
Câu 2 tương tự như câu 1
A=\(\left(1+1+1+1\right)\)-\(\left(\frac{1}{10}+\frac{1}{40}+...+\frac{1}{154}\right)\)
A= 4 -\(\left(\frac{1}{2.5}+\frac{1}{5.8}+...+\frac{1}{11.14}\right)\)
Bạn tự làm tiếp
Câu 3,4,5 tách giống nhau mk làm 1 ý nha !
3, A =\(\left(1-\frac{1}{3}\right)\)+\(\left(1-\frac{1}{15}\right)\)+....+\(\left(1-\frac{1}{9999}\right)\)
A= \(\left(1+1+1+...+1\right)\)-\(\left(\frac{1}{3}+\frac{1}{15}+...+\frac{1}{9999}\right)\)
Bạn làm nốt nha !
