=> A = 6/3.( 1/15 - 1/18 + 1/18 - 1/21 + ..... + 1/87 - 1/90 )
=> A = 2.( 1/15 - 1/90 )
=> A = 2.5/90
=> A = 10/90 = 1/9
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tính 6/15.18+6/18.21+6/21.24+...+6/87.90
6/15.18 + 6/18.21 + 6/21.24 + ...+ 6/87.90
Tính nhanh:
B= 6/1.3 + 6/3.5 + 6/5.7 + 6/7.9 + .....+ 6/99.101
C= 6/15.18 + 6/ 18.21 + 6/21.24+ ......+ 6/87.90
Tính tổng:
a)A=6/15.18+6/18.21+6/21.24+....+6/87.90) b) B= 1/10+1/15+1/21+....+1/120
B=2/15+2/35+2/63+....+2/399
c=7/10.11+7/11.12+7/12.13 + .....+7/69.70
D=6/15.18 + 6/ 18.21+6/21.24 +...+6/87.90
Tính nhanh M=\(\frac{6}{15.18}\)+\(\frac{6}{18.21}\)+\(\frac{6}{21.24}\)+........+\(\frac{6}{87.90}\)
1/15.18+1/18.21+1/21.24+..+1/87.90
tính nhanh
Tính tổng:
a) A = \(\frac{1}{2}\)+ \(\frac{1}{2.3}\)+ \(\frac{1}{3.4}\)+ .... + \(\frac{1}{23.24}\)
b) B = \(\frac{6}{15.18}\)+ \(\frac{6}{18.21}\)+ \(\frac{6}{21.24}\)+ .... + \(\frac{6}{87.90}\)
A = 9/15.18 + 9/18.21 + 9/21.24 + ......+ 9/87.90
Ai nhanh mink tick cho