แล้วทำไมไม่ทำแบบที่เคยทำครับ
$\lim_{x\to\infty}(\frac{x^2}{x-1}-\frac{x^2}{x+1})$
$\lim_{x\to\infty}(\frac{\infty^2}{\infty-1}-\frac{\infty^2}{\infty+1}) = \lim_{x\to\infty}(\infty-\infty)$
หรือทำแบบนี้
$\lim_{x\to\infty}(\frac{1}{\frac{1}{x} -\frac{1}{x^2}}-\frac{1}{\frac{1}{x} +\frac{1}{x^2}}) = \lim_{x\to\infty}(\frac{1}{0 -0}-\frac{1}{0 +0}) = \infty-\infty$
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