Tùng:20 cái bánh

Nam:40 cái bánh

Hok tốt!

a/

\(\left(2x+1\right)^3=125=5^3\)

\(\Rightarrow2x+1=5\Rightarrow x=2\)

b/

\(64.4^x=4^5\Leftrightarrow4^3.4^x=4^5\)

\(\Leftrightarrow4^{x+3}=4^5\Rightarrow x+3=5\Rightarrow x=2\)

`(2x+1)^3 = 125

`(2x+1)^3 = 5^2`

`2x+1=5`

`2x=5-1`

`2x=4`

`x=4:2`

`x=2`

Vậy `x = 2`

_____________________________

`64.4^x = 4^5`

`4^x  = 4^5 : 64`

`4^x = 4^5 : 4^3`

`4^x= 4^2`

`=> x = 2`

12+x = 921 - 18

12+x = 903

      x= 903 - 12

     x = 891

12+ x +24 +18 = 92

(12+24+18) + x = 92

                54 +x = 92

                       x= 92 -54

                      x= 38

`12 + x + 18 = 921`

`12+x = 921 - 18`

`12+x = 903`

`x= 903 - 12`

`x = 891`

Vậy `x = 891`

`12+ x +24 +18 = 92`

`12+24+18 + x = 92`

`54 +x = 92`

`x= 92 -54`

`x= 38`

Vậy `x = 38`

1233; 1323; 1332; 2133; 2313; 2331; 3123; 3132; 3213; 3231; 3312; 3321

1233; 1323; 1332; 2133; 2313; 2331; 3123; 3132; 3213; 3231; 3312; 3321

\(\dfrac{4}{5}\) = \(\dfrac{4\times8}{5\times8}\) = \(\dfrac{32}{40}\) ; \(\dfrac{4}{6}\) = \(\dfrac{4\times8}{6\times8}\) = \(\dfrac{32}{48}\)

5 phân số nằm giữa \(\dfrac{4}{5}\) và \(\dfrac{4}{6}\) là \(\dfrac{32}{41}\); \(\dfrac{32}{42}\); \(\dfrac{32}{43}\); \(\dfrac{32}{44}\); \(\dfrac{32}{45}\); \(\dfrac{32}{46}\); \(\dfrac{32}{47}\)

`52/7` + `31/4` - `25/8`

= `52xx8/7xx8` + `31xx14/4xx14` - `25xx7/8xx7`

= `416/56` + `434/56` - `175/56`

= `416+434-175/56`

= `675/56`.

Mắ sao nó cứ bị điên điên khùng khùng như này mãi thế nhờ??