A

A

đầu bài: 1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20

= (1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+20

=    20   +   20   +   20   +    20  +   20  +    20  +   20   +   20   +   20   +20

=   20.10

=   200

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20=\(\frac{\left(1+20\right)20}{2}\)=210

\(\dfrac{55}{56};\dfrac{8}{9};\dfrac{3}{4};\dfrac{7}{6}\)

55/56

3/4

7/6

8/9

1+2+3+4+....-56+56+48.......-23+56+586=6928

=6978 nha bn 

300

465 

\(a,ƯC\left(40,24\right)=Ư\left(8\right)=\left\{...\right\}\\ b,ƯC\left(12,52\right)=Ư\left(4\right)=\left\{...\right\}\\ c,ƯC\left(36,990\right)=Ư\left(18\right)=\left\{...\right\}\\ d,ƯC\left(54,36\right)=Ư\left(9\right)=\left\{...\right\}\\ e,ƯC\left(10,20,70\right)=Ư\left(10\right)=\left\{...\right\}\\ f,ƯC\left(25,55,75\right)=Ư\left(5\right)=\left\{...\right\}\\ g,ƯC\left(80,144\right)=Ư\left(16\right)=\left\{...\right\}\\ h,ƯC\left(63,2970\right)=Ư\left(9\right)=\left\{...\right\}\\ i,ƯC\left(65,125\right)=Ư\left(5\right)=\left\{...\right\}\\ j,ƯC\left(9,18,72\right)=Ư\left(9\right)=\left\{...\right\}\\ k,ƯC\left(24,36,60\right)=Ư\left(12\right)=\left\{...\right\}\\ l,ƯC\left(16,42,86\right)=Ư\left(2\right)=\left\{..\right\}\)

a:UC(40;24)=Ư(8)

b: UC(12;52)=Ư(4)

5, 31+1240++1829=3100

6. -19+836+1829=2646

7.  54.43-32.35=2322-1120=1202

8 2018(31+16+50)=2018.97=195746

9. 16(34-21+55)=16.68=1088

10. 63(29-31-98)=63.(-100)=-6300

cả lời giải thì

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