b) Ta có: 19.(2+3+4-5+6-7)^2-9.(7x-2)=0
Simplifying the expression inside the parentheses, we get: 19.(3)^2-9.(7x-2)=0
Simplifying further, we have: 19.(9)-9.(7x-2)=0
Expanding, we get: 171-63x+18=0
Combining like terms, we have: -63x+189=0
Subtracting 189 from both sides, we get: -63x=-189
Dividing both sides by -63, we get: x=3

c) Ta có: 3.(2x+1)^3=81
Dividing both sides by 3, we get: (2x+1)^3=27
Taking the cube root of both sides, we get: 2x+1=3
Subtracting 1 from both sides, we get: 2x=2
Dividing both sides by 2, we get: x=1

d) Ta có: (x+1)^5=243
Taking the fifth root of both sides, we get: x+1=3
Subtracting 1 from both sides, we get: x=2

Vậy giá trị của x là: x=3 (b), x=1 (c), x=2 (d).