???

2^a-1.7^b+1=28^a+b

=> 2^a-1.7^b+1=(4.7)^a+b

=> 2^a-1.7^b+1=4^a+b.7^a+b

=> 2^a-1.7^b+1=(2²)^a+b.7^a+b

=> 2^a-1.7^b+1=2^2(a+b).7^a+b

=> +) 2^a-1=2^2(a+b)

=> a-1=2(a+b)

+) 7^b+1=7^a+b

=> b+1=a+b

=> a=1

Mà a-1=2(a+b)

=> 1-1=2(1+b)

=> 0=2.(1+b)

=> 1+b=0

=> b=-1

Vậy a=1; b=-1.

\(\)108km/h \(\approx\) 30,24m/s

Thời gian bóng bay là:

30 : 30,24 = 0,9(920634)

Vậy...............................................

a) Trị tuyệt đối?

\(\left|x\right|=0,37\Rightarrow\left\{{}\begin{matrix}x=-0,37\\x=0,37\end{matrix}\right.\)

b) \(\dfrac{x}{169}=\dfrac{104}{x}\Rightarrow x^2=169.104=17576\)

\(\Rightarrow\left[{}\begin{matrix}x=\sqrt{17576}=26\sqrt{26}\\x=-\sqrt{17576}=-26\sqrt{26}\end{matrix}\right.\)

c) \(\dfrac{x+9}{15}=\dfrac{3}{5}\Rightarrow5\left(x+9\right)=45\)

\(\Rightarrow x+9=9\Rightarrow x=0\)

\(P=\dfrac{14-x}{4-x}=\dfrac{\left(4-x\right)+10}{4-x}=1+\dfrac{10}{4-x}\)

Ta có: \(\dfrac{10}{4-x}\ge10\forall x\)

\(\Rightarrow P\ge11\forall x\)

Vậy Min_(P) là 11 khi x = 3

3 it is fifteen past eleven------it is .....eleven fifteen.............

I amin class 6a-------which.........class are you in?......................

it is a quarter to nine-------it is..........eight forty- five...........

classes finish at eleven-----classes...end at eleven......................

\(A=\left(3,1-2,5\right)-\left(-2,5+3,1\right)\)

\(=3,1-2,5+2,5-3,1=0\)

\(B=\left(5,3-2,8\right)-\left(4+5,3\right)\)

\(=5,3-2,8-4-5,3=-6,8\)

\(C=-\left(251.3+281\right)+3.215-\left(1-281\right)\)

\(=-753-281+645-1+281\)

\(=-753+654-1=-100\)

\(D=-\left(\dfrac{3}{5}+\dfrac{3}{4}\right)-\left(\dfrac{-3}{4}+\dfrac{2}{5}\right)\)

\(=-\dfrac{3}{5}-\dfrac{3}{4}+\dfrac{3}{4}-\dfrac{2}{5}=\dfrac{-3}{5}-\dfrac{2}{5}=-1\)

Gọi A = \(\dfrac{1}{1.3}+\dfrac{1}{3.5}+\dfrac{1}{5.7}+...+\dfrac{1}{49.51}\)

\(\Rightarrow2A=\)\(\dfrac{2}{1.3}+\dfrac{2}{3.5}+\dfrac{2}{5.7}+...+\dfrac{2}{49.51}\)

\(\Rightarrow2A=\dfrac{1}{1}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{49}-\dfrac{1}{51}\)

\(\Rightarrow2A=\dfrac{1}{1}-\dfrac{1}{51}=\dfrac{50}{51}\)

\(\Rightarrow A=\dfrac{50}{51}:2=\dfrac{25}{51}\)

Vậy A = 0,(4901960784313725)

2.18.14 + 3.12.17 - 4.31.9

= 36.14 + 36.17 - 36.31

= 36. (14+17-31)

= 36. 0 =0

1 what is the time?-------what.........time is it....................?

2 it is six thirty?-----------it is..............half past six..............