limit as x approaches 129 of (x-129)/(sqrt(x+15)-12)

解答

x \to 129 lim (\frac{x - 129}{x + 15 - 12})

24

求解步骤

x \to 129 lim (\frac{x - 129}{x + 15 - 12})

\frac{x - 129}{x + 15 - 12}

分母有理化:

x + 15 + 12

= x \to 129 lim (x + 15 + 12)

代入值

x = 129

= 129 + 15 + 12

化简

129 + 15 + 12 : 24

= 24

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