1：分子分母同除以n*n，顯然答案是1/22:分子分母同時乘以5，顯然答案是53：由基礎極限公式sinx/x=1,令x=3x可得答案是c4:顯然x=2在0處無定義，所以當x不等於0時，f（x）=x-2，所以顯然是可去間斷點B簡單吧，都是一眼能看出來的

(1) y"" = 2, y" = 2x+C1, y = x^2+C1x+C2

(2) y"" = 2x, y" = x^2+C1, y = (1/3)x^3+C1x+C2

(3) y"" = sinx, y" = -cosx+C1, y = -sinx + C1x+C2

(4) y"" = e^(2x), y" = (1/2)e^(2x) + C!, y = (1/4)e^(2x) + C1x + C2

(5) 特徵方程：r^2-4r+3 = 0, r = 1, 3, 通解 y = C1e^x + C2e^(3x)

(6) 特徵方程：r^2-2r+1 = 0, r = 1, 1, 通解 y = (C1+C2x)e^x

(7) 特徵方程：r^2-6r= 0, r = 0, 6, 通解 y = C1 + C2e^(6x)