20 . 1000 = 20000

20 . 100 = 2000

20.1000=20000

20.100=2000

20000 và 2000 nhoa

\(=\dfrac{2^{36}.3^{36}\left(2.5^2.5^{40}-2.5.5^{34}\right)}{2^{30}.3^{30}.5^{30}.2^4.5^4\left(2^2.5^2.3^5.5^5-2^2.3^5\right)}=\dfrac{2^{36}.3^{36}\left(2.5^{42}-2.5^{35}\right)}{2^{34}.3^{30}.5^{34}\left(2^2.3^5.5^7-2^2.3^5\right)}\)

\(=\dfrac{2^2.3^6.2.5^{35}\left(5^7-1\right)}{2^2.3^5\left(5^7-1\right)}=3.2.5^{35}=6.5^{35}\)

\(20.100+10.200-10.200\)

\(=2000+0\)

\(=2000\)

Chúc bạn học tốt

20 . 100 + 10 . 200 - 10 . 200

= 20 . 100 + 10 . 2 . 100 - 10 . 2 . 100

= 20 . 100 + 20 . 100 - 20 . 100

= 20 ( 100 + 100 - 100 )

= 20 . 100

= 2000

20 x 100 + 10 x 200 - 10 x 200

=>  20 x 100 ( bỏ 10 x 200 vì cộng rồi lại trừ nên có thể bỏ )

=    2000

1000.1000.1000:2000+5000+8000:20.10 = 1000 000 .1/2 + 5000 + 400.10

= 500 000 + 5000 + 4000 = 509 000

Thưa sếp , không làm được .

\(\text{15.(-176)+15.76+100.15}\)

\(=15.\left(-176+76+100\right)\)

\(=15.0\)

\(=0\)

\((-18)+(-31)+98+\left|-18\right|+(-69)\)

\(=(-18)+(-31)+98+18+(-69)\)

\(=(-18)+18+(-31)+(-69)+98\)

\(=0+(-100)+98=-2\)

\(17(15-16)+16(17-20)\)

\(=17\cdot15-17\cdot16+16\cdot17-16\cdot20\)

\(=17\cdot15-16\cdot20\)

\(=-65\)

A=20/1.21+20/2.22+...+20/80.100

=1-1/21+1/2-1/22+...+1/80-1/100

=(1+1/2+...+1/80)-(1/21+1/22+...+1/100)

80B=80/1.81+80/2.82+...+8/20.100

=1-1/81+1/2-1/82+...+1/20-1/100

=(1+1/2+...+1/20)-(1/81+1/82+...+1/100)

=(1+1/2+1/3+...+1/20+1/21+1/22+...+1/80)-(1/21+1/22+...1/80+1/81+1/82+...1/100)

=>20A=80B

=>A=4B