\(\Leftrightarrow C=\frac{2\cdot30^2\left(30^{28}+30^{24}+30^{20}+.....+30^4+1\right)}{45\left(30^{28}+30^{24}+30^{20}+.....+30^4+1\right)}=\frac{2\cdot900}{45}=40\)

thanks

x=17.17992192

3^x + 25 = 26 . 2² + 2 . 30

=> 3^x + 25 = 26 . 4 + 60

=> 3^x + 25 = 164

=> 3^x = 164 - 25

=> 3^x = 139

=> Không tồn tại bất cứ giá trị x nào thỏa mãn

(Đề có sai không?)

(2x + 1)³ = 343

=> (2x + 1)³ = 7³

=> 2x + 1 = 7

=> 2x = 7 - 1

=> 2x = 6

=> x = 6 : 2

=> x = 3

3^x + 25 = 26 . 2² = 2 . 30

=> 3^x + 25 = 26 . 4

=> 3^x + 25 = 104

=> 3^x = 104 - 25

=> 3^x = 79

x = ...

=.= đề sai rồi

anh chả hiểu

(\(\frac{25}{5^2}\times30\)) : 15 x 7

= (1 x 30) : 15 x 7

= 30 : 15 x 7

= 2 x 7

= 14

\(15x^2+30=0\\ \Rightarrow x^2+2=0\left(vô.lí\right)\\ \Rightarrow x\in\varnothing\)

\(\left(2x-1\right)^2.4=1\\ \Rightarrow\left(2x-1\right)^2=\dfrac{1}{4}\\ \Rightarrow\left[{}\begin{matrix}2x-1=\dfrac{1}{2}\\2x-1=-\dfrac{1}{2}\end{matrix}\right.\\ \Rightarrow\left[{}\begin{matrix}x=\dfrac{3}{4}\\x=\dfrac{1}{4}\end{matrix}\right.\)

Câu a:

25% - 5/4 + 1 5/6

= 1/4 - 5/4 + 11/6

= -1 + 11/6

= - 6/6 + 11/6

= 5/6

Câu b:

75% : 2 1/5 - (0,5)^2.(-7) + 2,5.(7 2/3 - 5 2/3)

= 3/4 : 11/5 + 1/4.7 + 2,5.2

= 3/4 x 5/11 + 7/4 + 5

= 15/44 + 7/4 + 5

= 15/44 + 77/44 + 220/44

= 92/44 + 220/44

= 312/44

= 78/11

15 x 2 - 15 x 8

3 + 42

    15 x ( 2 - 8 ) 

    45

= -6    /3

= -2

15 + 15x2 + 15x7 -100

= 15 x( 1+2+7 ) -100

= 15 x 10 -100

= 150-100

=50

15 + 15 x 2 + 15 x 7 - 100

= ( 2 + 7 + 1 ) x 15

= 10 x 15

= 150

= 15 x 2^50 + 3 x 2^50 x 4 - (2^48 x 1 + 13 x 2^48)

= (15 + 3 x 4) x 2^50 - (13 + 1) x 2^48

= 27 x 2^50 - 14 x 2^48

= 27 x 4 x 2^48 - 14 x 2^48

= (108 - 14) x 2^48

= 94 x 2^48 

= 47 x 2 x 2^48 

= 47 x 2^49