1+1+1+1+1+1+1+1+1+1+1+1x101
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Tìm X biết (1/1x101+1/2x102+...+1/10x110)xX=1/1x11+1/2x12+...+1/100x110)
Cho A = 1/1x101 + 1/2x102 + 1/3x103 + ... + 1/25x125
B = 1/1x26 + 1/2x27 + 1/3x28 + ... + 1/100x125
tìm thương A/B
Ta có:
A=\(\frac{1}{1.101}+\frac{1}{2.102}+...+\frac{1}{25.125}\)
=\(\frac{1}{100}\left(\frac{100}{1.101}+\frac{100}{2.102}+...+\frac{100}{25.125}\right)\)
=\(\frac{1}{100}\left(1-\frac{1}{101}+\frac{1}{2}-\frac{1}{102}+...+\frac{1}{25}-\frac{1}{125}\right)\)
=\(\frac{1}{100}\left[\left(1+\frac{1}{2}+...+\frac{1}{25}\right)-\left(\frac{1}{101}+\frac{1}{102}+...+\frac{1}{125}\right)\right]\)
B=\(\frac{1}{1.26}+\frac{1}{2.27}+...+\frac{1}{100.125}\)
=\(\frac{1}{25}\left(\frac{25}{1.26}+\frac{25}{2.27}+...+\frac{25}{100.125}\right)\)
=\(\frac{1}{25}\left(1-\frac{1}{26}+\frac{1}{2}-\frac{1}{27}+...+\frac{1}{100}-\frac{1}{125}\right)\)
=\(\frac{1}{25}\left[\left(1+\frac{1}{2}+...+\frac{1}{100}\right)-\left(\frac{1}{26}+\frac{1}{27}+...+\frac{1}{125}\right)\right]\)
=\(\frac{1}{25}\left[\left(1+\frac{1}{2}+...+\frac{1}{25}\right)+\left(\frac{1}{26}+\frac{1}{27}+...+\frac{1}{100}\right)-\left(\frac{1}{26}+\frac{1}{27}+...+\frac{1}{100}\right)-\left(\frac{1}{101}+\frac{1}{102}+...+\frac{1}{125}\right)\right]\)
= \(\frac{1}{25}\left[\left(1+\frac{1}{2}+...+\frac{1}{25}\right)-\left(\frac{1}{101}+\frac{1}{102}+...+\frac{1}{125}\right)\right]\)
=> \(\frac{A}{B}\)=\(\frac{\frac{1}{100}\left[\left(1+\frac{1}{2}+...+\frac{1}{25}\right)-\left(\frac{1}{101}+\frac{1}{102}+...+\frac{1}{125}\right)\right]}{\frac{1}{25}\left[\left(1+\frac{1}{2}+...+\frac{1}{25}\right)-\left(\frac{1}{101}+\frac{1}{102}+...+\frac{1}{125}\right)\right]}\)=\(\frac{1}{\frac{100}{\frac{1}{25}}}\)=\(\frac{1}{100}\cdot25=\frac{25}{100}=\frac{1}{4}\)
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tìm x
a ,x-7/4+x-6/3+x-5/3+x+81/7=0
b,x-1/2013+x-2/2012+x+3/2011+...+x-2012/2=2012
c(1/1x101=1/2x102+1/3x103+1/4x164+1/10x110)x X =(1/1x11+1/2x12+...+1/100x110)
ai nhanh mình tick
a) Tính hợp lí các tổng sau:
S1: 1/14+1/35+1/65+.....+1/350
S2: 1/3+1/32+1/33+1/34+.....+1/3300
S3:1/1x3x5+1/3x5x7+1/5x7x9+....+1/25x27x29
S4:1+1/2+1/4+1/8+....+1/1024
b) Tìm x biết
(1/1x101+1/2x102+....+1/10x110)x=1/1x11+1/2x12+...+1/100x110
Cho A frac{1}{1x101} + frac{1}{2x102} + frac{1}{3x103} + . . . + frac{1}{25x125} B frac{1}{1x26} + frac{1}{2x27} + frac{1}{3x28}+. . . + frac{1}{100x125} Trong đó A có 25 số hạng , B có 100 số hạng . Tìm thương A : B Nhanh lên nhé mk cần khẩn cấpAi đúng mk tick cho
Đọc tiếp
Cho A = \(\frac{1}{1x101}\) + \(\frac{1}{2x102}\) + \(\frac{1}{3x103}\) + . . . + \(\frac{1}{25x125}\)
B = \(\frac{1}{1x26}\) + \(\frac{1}{2x27}\) + \(\frac{1}{3x28}\)+. . . + \(\frac{1}{100x125}\)
Trong đó A có 25 số hạng , B có 100 số hạng . Tìm thương A : B
Nhanh lên nhé mk cần khẩn cấp
Ai đúng mk tick cho
Tính A biết
A = \(\frac{1}{1x101}\)+ \(\frac{2}{2x102}\)+ \(\frac{3}{3x103}\)+ ... + \(\frac{25}{25x125}\)
A = \(\frac{1}{101}+\frac{1}{102}+\frac{1}{103}+...+\frac{1}{125}\)
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\(A=\frac{1}{101}+\frac{1}{102}+\frac{1}{102}+...+\frac{1}{125}\)
( Nếu muốn dùng thử lại : )
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