bài 1: tìm x biết x \(\in\) N
a, \(\dfrac{4^5+4^5+4^5+4^5}{3^5+3^5+3^5+3^5}\) \(\times\) \(\dfrac{6^5+6^5+6^5+6^5+6^5+6^5}{2^5+2^5+2^5+2^5+2^5+2^5}\) = 2x
b, (x - 1)x+2 = (x - 1)x+4
c, 6. (6 - x)2003 = (6 - x)2003
d, 411 . 2511 \(\le\) 2x . 5x < 2012 . 512