C=2/1.4+2/4.7+2/7.10+.......+2/61.64
S=1.4+4.7+7.10+10.13+...+61.64
A = 15/1.4 + 15/4.7 + 15/7.10+...+15/61.64 =?
So sánh A với 1, biết A= 3/1.4+3/4.7+3/7.10+....+3/61.64+3/64.67
( 31/1.4= 31 trên 3.4)
bai 1 ]
A, tinh nhanh 16 + (27-7.6) - (94.7-27.99)
B, tinh tong A= 2/1.4 + 2/ 4.7+ 2/7.10 +.....+ 2/97.100
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M = \(\dfrac{-3}{1.4}-\dfrac{3}{4.7}-\dfrac{3}{7.10}-...-\dfrac{3}{61.64}\)
bai1:tinh tong S=1.3+3.5+5.7+...+99.101
bai2 :tinh tong S=1.4+4.7+7.10+...+2017.2020
bai 3: tinh tong N=2.4+4.6+6.8+..+100.102
bai 4: tinh tóng=2.6+6.10+10.14+14.18+...+42.46+50.54
bai 5:tinh tongB=2^2+4^2+6^2+...+100^2
bai 6:C=1^2+3^2+...+100^2
bai7: biet 1^2+2^2+3^2+...+10^2=385 tinh tong 2^2+4^2+6^2+...+20^2
bai 8: tinh tong s=1^2+2^2+3^2+...+99^2
Tính A:
A= 1.42 + 4.72 + .................. + 61.642
a = 2/1.4+2/4.7 +4/7.10 +... + 2/97.100