Cho A = 1 + 3 + 32 + …+ 32006

a) Tính 3A

b) Chứng minh A = (32007 – 1):2

Bài 6. Tìm x  Z, sao cho:

a. (x – 3) – 12 = – 25

f. 121 – (35 – x) = 2.52

c. 72 – (84 – 9x) : 7 = 69

g. 2(17 + x) – (400 – 325) = – 31

d. (x + 7).(x – 5) =0

h. (x – 10).(x2 – 9) = 0

e. (x + 8).(x2 + 1) = 0

i. 17 – { – x + [– x – (– x)]} = – 16

Bài 5.Tìm x N, sao cho:

a)3636 : (12x –91) = 36

b)(x : 23 + 45) . 67 = 8911

c)[(6x –39) : 7]. 4 = 12

d)(3x –24). 73= 2. 74

e)x(x –10) = 0

f)(x+ 1). (x –2) = 0

g)(9 –x)3= 64

h)3x= 81

i)2 . 3x= 10 . 312+ 8 . 312

j)(19x + 2.52) : 14 = (13 -8)2-42

alo