giúp tui viết cả lời giải nữa tui sắp nộp zùi ai trả lời đúng tui k 3 cái cho

trả lời :

1 + 1 = 2

2 + 2 = 4

1+1=2

2+2=4

1 + 1 = 2 

2 + 2 = 4

(1+\(\frac{1}{6}\) ) + (\(\frac{1}{2}\) + \(\frac{1}{5}\) ) + (\(\frac{1}{3}\)+ \(\frac{1}{4}\))

= \(\frac{7}{1.6}\) + \(\frac{7}{2.5}\) + \(\frac{7}{3.4}\)

= 7(\(\frac{1}{1.6}\) + \(\frac{1}{2.5}\) + \(\frac{1}{3.4}\)) chia hết cho 7 => đpcm

sai đề

1 + ( 1/2+1/3+1/4+1/5 +1/6)=1+29/20=49/20=7.7/20=7. 7/20chia hết cho 7 nên ....

Đầu bài thế này thì tìm x đến tết chả hết

\(a,\dfrac{1}{2}-\dfrac{1}{3}-\left(-\dfrac{5}{4}\right)=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{5}{4}=\dfrac{1\times6-1\times4+5\times3}{12}=\dfrac{6-4+15}{12}=\dfrac{17}{12}\\ b,\dfrac{5}{4}-\dfrac{1}{2}-\dfrac{7}{8}=\dfrac{5\times2-1\times4-7}{8}=\dfrac{10-4-7}{8}=-\dfrac{1}{8}\\ c,\dfrac{1}{5}-\dfrac{1}{2}+\dfrac{9}{10}=\dfrac{1\times2-1\times5+9}{10}=\dfrac{2-5+9}{10}=\dfrac{6}{10}=\dfrac{3}{5}\\ d,\dfrac{5}{4}-\dfrac{1}{3}+\dfrac{7}{6}=\dfrac{5\times3-1\times4+7\times2}{12}=\dfrac{15-4+14}{12}=\dfrac{25}{12}\)

`1/2+(-1/3)-(-5/4)`

`=1/2-1/3+5/4`

`=3/6-2/6+5/4`

`=1/6+5/4`

`=2/12+15/12`

`=17/12`

__

`5/4-1/2+(-7/8)`

`=5/4-1/2-7/8`

`=10/8-4/8-7/8`

`=6/8-7/8`

`=-1/8`

__

`1/5-1/2+9/10`

`=2/10-5/10+9/10`

`=-3/10+9/10`

`=6/10`

`=3/5`

__

`5/4-1/3+7/6`

`=15/12-4/12+14/12`

`=11/12+14/12`

`=25/12`

`#lv`

2ⁿ=2^n-1+2^n-1

2ⁿ=2ⁿ:2¹+2ⁿ:2¹

2ⁿ=(2ⁿ+2ⁿ):2¹

2ⁿ=(2ⁿ+2ⁿ):2

2ⁿ=2ⁿ.2:2

2ⁿ=2ⁿ( đpcm)

\(2^n=2^{n-1}+2^{n-1}\)

\(2^n=2.2^{n-1}\)

\(2^n=2^n\)(luôn đúng)

suy ra đpcm