Tìm x: a) (x+6)^5=(x+6)^4, b) (x-12)^12=(x-12)^10

Tìm x:

a) (x+6)^5=(x+6)^4

b) (x-12)^12=(x-12)^10

c) (x+3)^7=5.(x+3)^6

d) (x-4)^3= 4.(x-4)