57/12 = 114/24

57/13= 114/26

Mà 114/x như trên nên x=25

Cảm ơn bạn !

18B

19B

a ) x = 5 6 ; b ) x = 8 7 ; c ) x = − 11 14 − ; d ) x = − 13 12

Có số số hạng là:

\(\frac{61-5}{4}+1=15\)(số)

Ta có: ( X + 5) + ( X + 9) + (X + 13) + ….+ ( X + 57) + (X + 61) = 1035

=>15X + \(\frac{ \left(5+61\right).15}{2}\)=1035

=>15X + 495 = 1035

=>15X = 1035 - 495 = 540

=>x = 540 : 15

=> x=36

**** đi Hiếu

\(5^{x-1}-13=612\)

\(\Leftrightarrow5^{x-1}=625\)

\(\Leftrightarrow5^{x-1}=5^4\)

\(\Leftrightarrow x-1=4\)

\(\Leftrightarrow x=5\)

5^x-1 - 13 = 612

5^x-1 = 612 + 13

5^x-1 = 625

5^x-1 = 5⁴

x+ 1 = 4

x = 4 - 1

x = 3

5x - 13 = 612

5x = 612 + 13

5x = 625

x = 625 : 5

x = 125

Vậy x = 125

5x-1-13=612

5x-1=612+13

5x-1=625

5x=625+1

5x=626

x=626:5

x=125,2

5^x-1 - 13 = 612

5^x-1 = 612 + 13

5^x-1 = 625

5^x-1 = 5⁴

x - 1 = 4

x = 4 - 1

x = 3

Vậy x = 3

a) Ta có x thuộc B(4)

=> B(4) = {0;4;8;12;16;20;24;28;32;36;40;44;48;52;56;60;...}

Mà 8 \(\le\)x \(\le\)57 => x \(\notin\){0;4;60}

Vậy x \(\in\){8;12;16;20;....;56}

b) Vì x \(⋮\)12 nên x \(\in\)B(12) = {0; 12 ; 24;36;48;60;72;84;96;108;...}

Mà \(0< x\le105\)nên x \(\in\){12;24;...;96}

cảm ơn bạn huỳnh quang sang ạ

43 x 57 + 43 x 156 - 43 x 144

= 43 x (57 + 156 - 144)

= 43 x 69

= 43 x ................

Mình giải đúng , chính xác va la dau tien ne !

Kquả là 2910

K Mk nhe!!! 

tính sao zậy ? chỉ coi

Cái này bạn áp dụng cộng dãy số cách đều là ra à

Số số hạng là: \(\dfrac{58-1}{1}+1=58\left(số\right)\)

Tổng của dãy là; \(\dfrac{58\left(58+1\right)}{2}=29\cdot59=1711\)

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