>>478 (下)
 X = x - 1/4 とおく。
 (左辺) = x^4 - x^3 + x^2 - x + (21/64)
   = X^4 + (5/8)X^2 - (5/8)X + (33/256)
   = (X^2 - 1/8)^2 + (7/8)X^2 - (5/8)X + (33/256)
   = (X^2 - 1/8)^2 + (7/8)(X - 5/14)^2 + (3/1792)
   > 3/1792,

感嘆で内科医?