M = (8x6 - 27) : (4x4 + 6x2 + 9)
= (2x2 - 3)(4x4 + 6x2 + 9) : (4x4 + 6x2 + 9)
= 2x2 - 3
N = (y4 - 1) : (y3 + y2 + y + 1)
= (y2 + 1)(y - 1)(y + 1) : [(y + 1)(y2 + 1)]
= y - 1
\(\frac{M}{N}=\frac{2x^2-3}{y-1}=\frac{2\cdot8^2-3}{251-1}=\frac{125}{250}=\frac{1}{2}\)