limit as x approaches infinity of (5^{x+1})/(e^x)

解答

x \to \infty lim (\frac{5 ^{x + 1}}{e ^{x}})

\infty

求解步骤

x \to \infty lim (\frac{5 ^{x + 1}}{e ^{x}})

化简

5^{x + 1} : 5^{x} \cdot 5

= x \to \infty lim (\frac{5 ^{x} \cdot 5}{e ^{x}})

x \to a lim [c \cdot f (x)] = c \cdot x \to a lim f (x)

= 5 \cdot x \to \infty lim (\frac{5 ^{x}}{e ^{x}})

使用指数法则:

\frac{a ^{c}}{b ^{c}} = (\frac{a}{b})^{c}

= 5 \cdot x \to \infty lim ((\frac{5}{e})^{x})

运用一般极限法则:

x \to \infty lim (a^{x}) = \infty, a > 1

= 5 \cdot \infty

运用无穷大属性:

c \cdot \infty = \infty

= \infty