a) 2x . 4 = 128
2x = 128 : 4
2x = 32
2x = 25 (vì 32 = 25)
x = 5
b) x15 = x
x15 - x = 0
x.(x14 -1) =0
x = 0 hoặc x14 = 1
x = 0 hoặc x = 1 hoặc x = -1
c) [2x + 1]3 = 53 (vì 125 = 53)
2x + 1 = 5
x = (5 - 1)/2
x = 2
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