`5^2 .(4-x)=625`

`25.(4-x)=625`

`4-x=625:25`

`4-x=25`

`x=4-25`

`x=-21`

Vậy `x=-21`

5² ( 4 - x ) = 625

25 ( 4 - x ) = 625

       4 - x = 625 : 25

       4 - x = 25

            x = 4 - 25 

            x = - 21

    75% - ( 1,25 - \(\dfrac{11}{4}\)) : \(\dfrac{9}{2}\)

=  \(\dfrac{75}{100}\) - (  \(\dfrac{125}{100}\)- \(\dfrac{11}{4}\)) : \(\dfrac{9}{2}\)

= \(\dfrac{3}{4}\) - (\(\dfrac{5}{4}\)- \(\dfrac{11}{4}\)) x \(\dfrac{2}{9}\)

= \(\dfrac{3}{4}\) + \(\dfrac{6}{4}\) x \(\dfrac{2}{9}\)

= \(\dfrac{3}{4}\)+ \(\dfrac{1}{3}\)

= \(\dfrac{13}{12}\)

`75% - (1,25 - 11/4) : 9/2`

`=75/100 - (5/4 - 11/4):9/2`

`=3/4  - (5/4 - 11/4):9/2`

`=3/4 - (-3/2): 9/2`

`=3/4 + 3/2 : 9/2`

`=3/4 + 3/2 xx 2/9`

`=3/4 + 1/3`

`=9/12 + 4/12`

`=13/12`

(4x-2)6=64

= (4x-2)6 = 26

= 4 x - 2 = 2

= 4 x = 2 + 2

= 4 x = 4

= x = 4 : 4

= x = 1

`(4x-2)^6 = 64`

`(4x-2)^6 = `\(\left(\pm2\right)^6\)

`@TH1:`

`4x-2=2`

`4x=2+2`

`4x=4`

`x=4:4`

`x=1`

`@TH2:`

`4x-2=-2`

`4x=-2+2`

`4x=0`

`x=0:4`

`x=0`

Vậy `x = {0;1}`

`(4x-2)^6 = 64`

`(4x-2)^6 = ` \(\left(\pm2\right)^6\)

`@TH1:`

`4x-2=2`

`4x=2+2`

`4x=4`

`x=4:4`

`x=1`

`@TH2:1`

`4x-2=-2`

`4x=-2+2`

`4x=0`

`x=0:4`

`x=0`

Vậy `x={0;1}`

( 4x - 2 )⁶ = 64 

( 4x - 2 )⁶ = 2⁶

4x - 2       = 2

4x            = 2 + 2

4x            = 4

x              = 1

5^{1 2} . 25⁴ . 125³ : 625

= 5¹² . 5⁸ . 5⁹ : 5⁴

= 5 ^{1 2 + 8 + 9 - 4} 

= 5²⁵

???

`6/8 = 15/x`

`3/4 = 15/x`

`x = 15 : 3/4`

`x=15 xx 4/3`

`x=20`

Vậy `x=20`

6/8=15/x

3/4=15/x

15/20=15/x

x=20

Số học sinh cả lớp là:

30 : 6/7 = 35 (học sinh)

Đáp số: 35 học sinh

a) 5³ . 2 - 100 : 4 + 2³ . 5

= 125 . 2 - 25 + 8 . 5

= 250 - 25 + 40

= 225 + 40

= 265

b) 6² : 9 + 50 . 2 - 3³ . 3

= 36 : 9 + 100 - 27 . 3

= 4 + 100 - 81

= 104 - 81 

= 23

c) 100 : 5² + 7 . 3²

= 100 : 25 + 7 . 9

= 4 + 63

= 67