定义域 f(x)=(4a^2-20a+25)/(25-4a^2)

解答

定义域

f (x) = \frac{4 a ^{2} - 20 a + 25}{25 - 4 a ^{2}}

a < - \frac{5}{2} or - \frac{5}{2} < a < \frac{5}{2} or a > \frac{5}{2}

间隔符号

(- \infty, - \frac{5}{2}) \cup (- \frac{5}{2}, \frac{5}{2}) \cup (\frac{5}{2}, \infty)

求解步骤

找到无定义的点（奇点）:

a = \frac{5}{2}, a = - \frac{5}{2}

函数定义域

a < - \frac{5}{2} or - \frac{5}{2} < a < \frac{5}{2} or a > \frac{5}{2}

d o main f (x) = \frac{2 x - 6}{x ^{2} - 4}

d o main y = 4 x^{2} - 9 + \frac{1}{x + 2}

d o main f (x) = - x - 1

d o main f (x) = 5^{x} + 2

d o main \frac{1}{- 4 x ^{2} - 20 x - 21}