\(\frac{2}{2}+\frac{2}{6}+\frac{2}{12}+\frac{2}{99\cdot100}\)

\(=\frac{2}{1\cdot2}+\frac{2}{2\cdot3}+\frac{2}{3\cdot4}+...+\frac{2}{99\cdot100}\)

\(=2\left(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{99\cdot100}\right)\)

\(=2\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{99}-\frac{1}{100}\right)\)

\(=2\left(\frac{1}{1}-\frac{1}{100}\right)\)

\(=2\cdot\frac{99}{100}\)

\(=\frac{99}{50}\)

2/2+2/6+2/12+...+2/99.100

= 2/3.4+2/3.4+....+2/99.100

=2/2.(2/2.3+2/3.4+....+2/99.100)

=1/2.(1/2.3+2/3.4+....+2/99.100)

=1/2.(1/2-1/3+1/3-1/4+....+1/99-1/100

=1/2.(1/2-1/100)

=1/2.49/100

=49/200

16:Sửa đề: \(\frac12x+\frac16\left(x-2\right)=\frac34-2x\)

=>\(\frac12x+\frac16x-\frac26=\frac34-2x\)

=>\(\frac46x-\frac13=\frac34-2x\)

=>\(\frac23x+2x=\frac34+\frac13\)

=>\(\frac83x=\frac{9}{12}+\frac{4}{12}=\frac{13}{12}\)

=>\(x=\frac{13}{12}:\frac83=\frac{13}{12}\times\frac38=\frac{13}{4\times8}=\frac{13}{32}\)

19: \(\frac{5}{12}x+3=\frac13-\frac{7}{12}x\)

=>\(\frac{5}{12}x+\frac{7}{12}x=\frac13-3\)

=>\(\frac{12}{12}x=\frac13-\frac93=-\frac83\)

=>\(x=-\frac83\)

20: \(\frac12x+\frac52=\frac72x-\frac34\)

=>\(\frac12x-\frac72x=-\frac34-\frac52\)

=>\(-3x=-\frac34-\frac{10}{4}=-\frac{13}{4}\)

=>\(3x=\frac{13}{4}\)

=>\(x=\frac{13}{4}:3=\frac{13}{12}\)

Trả lời:

1/2+1/4+1/8+1/16=8/16+4/16+2/16+1/16=15/16   (1)

1/2+1/6+1/12+...+1/132=1/(1.2)+1/(2.3)+1/(3.4)+...+1/(11.12)

=(1-1/2)+(1/2-1/3)+(1/3-1/4)+...+(1/11-1/12)

=1-1/12=11/12  (2)

 Từ (1) và (2) => (15/16) : (11/12) = 45/44

\(\frac{4^8.3^{12}.27^2}{6^{12}.9^3}\)

= \(\frac{\left(2^2\right)^8.3^{12}.27^2}{\left(2.3\right)^{12}.\left(3^2\right)^3}\)

= \(\frac{2^{16}.3^{12}.27^2}{2^{12}.3^{12}.27^2}\)

= \(\frac{2^{16}}{2^{12}}\)= 2⁴ = 16

(2.4.(-6)²):12

=(8.36):12

=288:12

=24.

#Học tốt.

Thay a=4, b=-6, c=12 ta đc

\(\left[2\cdot4\cdot\left(-6\right)^2\right]:12\)

\(=288:12\)

\(=24\)

vãi cả mình đang cần gấp . Trong khi thứ 2 mới học

ý a bạn nhé

`->D` 

vì : `4/16=(4:4)/(16:4)=1/4`

      `2/8=(2:2)/(8:2)=1/4`

      `3/12=(3:3)/(12:3)=1/4`

=3 nha bn

KANZAKI MIZUKI GIẢI TRINH TỰ HỘ MÌNH VỚI

\(M=2+2^2+2^3+...+2^{20}\\=(2+2^2)+(2^3+2^4)+(2^5+2^6)+...+(2^{19}+2^{20})\\=6+2^2\cdot(2+2^2)+2^4\cdot(2+2^2)+...+2^{18}\cdot(2+2^2)\\=6+2^2\cdot6+2^4\cdot6+...+2^{18}\cdot6\\=6\cdot(1+2^2+2^4+...+2^{18})\)

Vì \(6\cdot(1+2^2+2^4+...+2^{18})\vdots6\)

nên \(M\vdots6\)

Vậy \(M\vdots6\).