a=40

40+729+2187

d/s:2956

số các số hạng là : (2187 - 1): 2 +1 = 1094

a = (1+2187) x 1094 : 2 = 1196836

a,=>2⁰<2ⁿ<2⁷

=>0<n<7

=>n=1;2;3;4;5;6

vậy n=1;2;3;4;5;6

b,=>3²<3ⁿ<3⁶

=>2<n<6

=>n=3;4;5

vậy n=3;4;5

a) \(\Rightarrow2^0

a,  3 x + 1 : 3 4 = 81

3 x - 3 = 3 4

x – 3 = 4

x = 7

Vậy x = 7

b,  3 x + 3 . 3 x + 1 = 729

3 2 x + 4 = 3 6

2x + 4 = 6

x = 1

Vậy x = 1

c,  2 x + 3 . 2 x = 128

2 2 x + 3 = 2 7

2x + 3 = 7

x = 2

Vậy x = 2

d,  23 + 3 x = 5 6 : 5 3

23 + 3 x = 5 3

23 + 3x = 125

3x = 102

x = 34

Vậy x = 34

e,  2 x + 2 x + 4 = 272

2 x + 2 x . 2 4 = 272

2 x ( 1 + 2 4 ) = 272

2 x . 17 = 272

2 x = 16

2 x = 2 4

x = 4

Vậy x = 4

ta có \(\frac{a-1}{2}=\frac{b-2}{3}=\frac{c-3}{4}\Leftrightarrow\frac{2a-2}{4}=\frac{3b-6}{9}=\frac{c-3}{4}=\frac{2a-2+3b-6-c+3}{4+9-4}\)

         \(=\frac{\left(2a+3b-c\right)-\left(2+6-3\right)}{4+9-4}=\frac{50-5}{9}=\frac{45}{9}=5\)

                           \(\frac{2a-2}{4}=5\Rightarrow a=\frac{4.5+2}{2}=11\)

                          \(\frac{3b-6}{9}=5\Rightarrow b=\frac{5.9+6}{3}=17\)

                          \(\frac{c-3}{4}=5\Rightarrow c=5.4+3=23\)

Lời giải:

Đặt $\frac{a-1}{2}=\frac{b+3}{4}=\frac{c-5}{6}=k$

$\Rightarrow a=2k+1, b=4k-3, c=6k+5$.

Khi đó:

$5a-3b-4c=50$

$\Rightarrow 5(2k+1)-3(4k-3)-4(6k+5)=50$

$\Rightarrow -26k=56\Rightarrow k=\frac{-28}{13}$

Suy ra:

$a=2k+1=2.\frac{-28}{13}+1=\frac{-43}{13}$

$b=4k-3=4.\frac{-28}{13}-3=\frac{-151}{13}$

$c=6k+5=6.\frac{-28}{13}+5=\frac{-103}{13}$

3,5

56 : a -82 : 25 = 159 : 150 + 583 : 50

56: a - 82 : 25= 1,06+11,66

56:a-82:25= 12,72

56: a - 82= 12,72 x 25

56:a-82= 318

56: a = 318 + 82

56: a = 400

A = 56 : 400

A =0,14

Tick tớ v

3,5

9^a=729

=>9^a=9³

=>a=3

9^a=729=9³

=>a=3

9^a=729

9^a=9^3

suy ra : a=3

tick nhé