câu hỏi là :

câu hỏi là gì

\(~~~~hd~~~~\)

\(A=3+3^2+3^3+...........+3^{100}\)

\(\Rightarrow3A=3^2+3^3+3^4+.........+3^{101}\)

\(\Rightarrow3A-A=2A=3^{101}-3\Rightarrow A=\frac{3^{101}-3}{2}\)

3^a +1 = b^2 + 1

suy ra

3^a = b^2

ta có 3^2=3^2

mà 3^a = b^2

suy ra  a=2 

            b=3

 x - [( x - 7 ) + (x - 14 + 8 )] = 2x - 14

 x - [ x - 7 + x - 14 + 8 ] = 2x - 14

 x -  x + 7 - x + 14 - 8  = 2x - 14

x - x - x - 2x = -14 - 7 - 14 + 8

-3x = -27

=> x = 9

Vậy...

Chúc em học tốt!!!

x = 9 

#Pikachu:))#

\(Đặt:a=6a`;b=6b`\)

\(\Rightarrow ab=36a`b`=72\Leftrightarrow a`b`=2\Leftrightarrow\left(a`,b`\right)\in\left\{\left(1;2\right);\left(2;1\right)\right\}\)

\(\Leftrightarrow\left(a,b\right)\in\left\{\left(6;12\right);\left(12;6\right)\right\}\)

khó vậy 

a, /a-1/ -x + 1=0 

TH1: a - 1 = 0 => a = 1

TH2 : x +  1 = 0 =>x = -1 

Vậy \(x\in\left\{1;-1\right\}\)

c)

| x + 7 | = | x - 9 |

TH1: x + 7 = x - 9 

         0x = -16 => Vô nghiệm

TH2: x + 7 = -x + 9

             2x = 2

          => x = 1

Vậy x = 1

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a,16 X 50X-25X(-250)

=(16 X-25)X50X(-250)

=-400X50X-250

=-20000X-250

=5000000

b,-54X76+12X(-76)

=76X(-54-12)

=76X(-66)

=-5016

c,32X(-64)-64X68

=-64X(32+68)

=-64X100

=-6400

d,19X42.(-19)+38X5

=19X(42-1)+19X2X5

=19X41+19X10

=19X(41+10)

=19X51=969

a) 16.50.(-25).(-250)

=[16.(-25)].50.(-250)

=-400.50.(-250) 

=-20000.(-250) 

=5000000

b,-54.76+12.(-76)

=76.(-54-12)

=76.(-66)

=-5016

c,32.(-64)-64.68

=-64.(32+68)

=-64.100

=-6400

d,19.42.(-19)+38.5

=19.(42-1)+19.2.5

=19.(42-1)+19.(2.5)

=19.41+19.10

=19.(41+10)

=19.51

=969