không biết 

= (1-2) + ( 3 -4 ) + ..... + ( 145 - 146 ) + 147

= -1 + -1 + .... + -1 + 147

rồi bn tự áp dụng công thức :

\(SSH=\left(\right)SC-SĐ\left(\right):KHOẢNGCÁCH+1\)

Tổng = ( SĐ + SC) X SSH : 2

`(3x-3^4)*9^3=9^5`

`(3x-3^4)=9^5:9^3`

`(3x-3^4)=9^2`

`3x=9^2+3^4`

`3x=162`

`x=162:3`

`x=54`

`***2k10`

3x-3^4=9^5:9^3=81

3x=81+3^4=162

X=162:3=54

c= - 1/10 nha

-1/3;-1/2;-5/9;1/3;7/18;5/12

Xếp:

-1/3; -1/2; -5/9; 1/3; 7/18; 5/12

\(\dfrac{8}{x}=\dfrac{-2}{7}\)

\(\Rightarrow8\cdot7=-2x\)

\(\Rightarrow56=-2x\)

\(\Rightarrow x=56:\left(-2\right)\)

\(\Rightarrow x=-28\)

Ta có:  2/7 = 8/28

8/x = 8/28 suy ra x = 28

\(A=\dfrac{10^{12}+6}{10^{12}-11}\)

\(\Rightarrow A=\dfrac{10^{12}-11+17}{10^{12}-11}\)

\(\Rightarrow A=\dfrac{10^{12}-11}{10^{12}-11}+\dfrac{17}{10^{12}-11}\)

\(\Rightarrow A=1-\dfrac{17}{10^{12}-11}\)

\(B=\dfrac{10^{11}+5}{10^{11}-12}\)

\(\Rightarrow B=\dfrac{10^{11}-12+17}{10^{11}-12}\)

\(\Rightarrow B=\dfrac{10^{11}-12}{10^{11}-12}+\dfrac{17}{10^{11}-12}\)

\(\Rightarrow B=1-\dfrac{17}{10^{11}-12}\)

Vậy ta cần so sánh \(1-\dfrac{17}{10^{12}-11}\) và \(1-\dfrac{17}{10^{11}-12}\) 

Ta thấy \(\left(10^{12}-11\right)>\left(10^{11}-12\right)\) và 2 phân số trên cùng tử số 17 nên \(\dfrac{17}{10^{12}-11}< \dfrac{17}{10^{11}-12}\)

Vậy \(1-\dfrac{17}{10^{12}-11}>1-\dfrac{17}{10^{11}-12}\) hay \(A>B\)

Cảm ơn bạn nhé!

1:How long

2:What time

3:How

4:when

5:why

Ta có A = \(\dfrac{1}{42}+\dfrac{1}{56}+\dfrac{1}{72}+\dfrac{1}{90}+\dfrac{1}{110}+\dfrac{1}{132}\)

= \(\dfrac{1}{6\cdot7}+\dfrac{1}{7\cdot8}+\dfrac{1}{8\cdot9}+\dfrac{1}{9\cdot10}+\dfrac{1}{10\cdot11}+\dfrac{1}{11\cdot12}\)

= \(\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{10}+\dfrac{1}{10}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{12}\)

= \(\dfrac{1}{6}-\dfrac{1}{12}=\dfrac{1}{12}\) 

B = \(\dfrac{\dfrac{2}{29}-\dfrac{2}{39}+\dfrac{2}{49}}{\dfrac{23}{29}-\dfrac{23}{39}+\dfrac{23}{49}}=\dfrac{2\left(\dfrac{1}{29}-\dfrac{1}{39}+\dfrac{1}{49}\right)}{23\left(\dfrac{1}{29}-\dfrac{1}{39}+\dfrac{1}{49}\right)}=\dfrac{2}{23}\) 

Lại có \(\dfrac{2}{23}>\dfrac{2}{24}=\dfrac{1}{12}\) hay A < B

Vậy A < B

Cảm ơn bạn nhé!