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(2+4+...+16+18) x (45 x 3+ 5 x 45 - 90 x 4)
= A x (135 + 225 - 360)
= A x 0
= 0
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a, 298+132+237+868+763
= 298+(132+868)+(237+763)
=298+1000+1000
=298+1000×2
=298+2000
=2298
b, 35×68+35×31+35
=35×68+35×31+35×1
=35×(68+31+1)
=35×100
=3 500
c, 35×34+35×66
=35×(34+66)
=35×100
=3 500
d, ( 563+745)-(463+545)
= 563 + 745 - 463 - 545
= (563-463) + (745-545)
= 100 + 200
= 300
e, 73+86+968+914+3032
= 73+(86+914)+(968+3032)
=73+1000 + 4000
=73+5000
=5073
f, 4×8×25×1,25×27
= (4×25)×(8×1,25)×27
=100×10×27
=1000×27
=27 000
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18*(5773+2457)+5310*6
=18 *8230+53108*6
=18*(8230+53108)*6
=18*61238*6
=11102184*6
=6613104
k cho mình nha
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(D=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+...+\frac{1}{512}+\frac{1}{1024}\)
=> \(2D=1+\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+...++\frac{1}{256}+\frac{1}{512}\)
=> \(2D-D=\left(1+\frac{1}{2}+...+\frac{1}{512}\right)-\left(\frac{1}{2}+\frac{1}{4}+...+\frac{1}{1024}\right)\)
=> \(D=1-\frac{1}{1024}\)
b) \(Đ=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{18.19}+\frac{1}{19.20}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{18}-\frac{1}{19}+\frac{1}{19}-\frac{1}{20}\)
\(=1-\frac{1}{20}=\frac{19}{20}\)
a) D=\(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\dots+\frac{1}{512}+\frac{1}{1024}.\)
\(D=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{8}+\frac{1}{8}-\frac{1}{16}+\dots+\frac{1}{512}-\frac{1}{1024}\)
\(D=1-\frac{1}{1024}\)
\(D=\frac{1023}{1024}\)
\(Đ=\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\dots+\frac{1}{18\cdot19}+\frac{1}{19\cdot20}\)
\(Đ=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\dots+\frac{1}{18}-\frac{1}{19}+\frac{1}{19}-\frac{1}{20}\)
\(Đ=1-\frac{1}{20}\)
\(Đ=\frac{19}{20}\)
Phần c như kiểu sai đề chỗ cuối hay sao ấy.
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\(a,\)\(\frac{13}{18}\div\frac{5}{9}-1\)
\(=\frac{13}{18}\times\frac{9}{5}-1\)
\(=\frac{13}{10}-1\)
\(=\frac{3}{10}\)
\(b,\)\(3+\frac{9}{4}\div\frac{3}{5}\)
\(=\)\(3+\frac{9}{4}\times\frac{5}{3}\)
\(=\)\(3+\frac{15}{4}\)
\(=\frac{27}{4}\)
\(\frac{13}{18}\div\frac{5}{9}-1\)
\(=\frac{13}{10}-1\)
\(=\frac{3}{10}\)
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5+18-7 = 16
3/8+1/2-5/24=9/24 +12/24-5/24=16/24=2/3
(16+2/3):(16+2/3)=1
(120/24+9/24+432/24+12/24-168/24-5/24):(48/3+2/3)=-32/24:50/3=-4/3.3/50=-4/50=-2/25
k cho mik nha
=11137
là 11137 đó