① The power of  (x) =  / 178 + 1

① The power of  (x) =  / 178 + 1

①x²n+xn-1／9y²+¼n
= n(x²+x+1/4)-(1/3y)²
=n(x+1/2)²-(1/3y)²
Is the title wrong
② The tenth power of x plus the fifth power of x minus 2
=x^10+x^5-2
=(x^5+2)(x^5-1)

Given that f (x) is continuous in a neighborhood of x = 0, and f (0) = 0, limx → 0f (x) 1-cosx = 2, then f (x) ()
A. Nondifferentiable B. differentiable, and f ′ (0) ≠ 0C. Get the maximum D. get the minimum

Limx → 0f (x) 1-cosx = limx → 0f (x) 12x2 + O (x2) = 2, so in the x = 0 critical field, f (x) = x2 + O (x2) f '(x) = 2x + O (x) f' '(x) = 2 + O (1), so at the point x = 0, f' (0) = 0, f '' (0) = 2 ＞ 0, that is, at the point x = 0, the function f (x) gets the minimum

1/1×3+1/3×5+1/5×7+···+1/(2n-1)（2n+1）

1/﹙1×3﹚＋1/﹙3×5﹚＋1/﹙5×7﹚＋…… ＋1/﹙2n－1﹚﹙2n＋1﹚
＝1/2×[1－1/3＋1/3－1/5＋1/5－1/7＋…… ＋1/﹙2n－1﹚－1/﹙2n＋1﹚]
＝1/2×[1－1/﹙2n＋1﹚]
＝1/2×2n/﹙2n＋1﹚
＝n/﹙2n＋1﹚.