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Is 1/0 Infinity for Limits?

Published in Calculus Limits 2 mins read

No, 1/0 is undefined in standard arithmetic. However, the limit of 1/x as x approaches 0 can approach infinity, depending on the direction from which x approaches 0.

Here's a breakdown:

  • 1/0 in Basic Arithmetic: Division by zero is undefined. There is no number that, when multiplied by zero, gives you one.

  • Limits and Infinity: Limits describe the behavior of a function as its input approaches a certain value. We are not actually evaluating the function at that value, but rather getting arbitrarily close.

  • One-Sided Limits:

    • Limit as x approaches 0 from the right (positive side): lim (x→0⁺) 1/x = +∞. As x gets smaller and smaller positive numbers (e.g., 0.1, 0.01, 0.001), 1/x gets larger and larger, approaching positive infinity.

    • Limit as x approaches 0 from the left (negative side): lim (x→0⁻) 1/x = -∞. As x gets smaller and smaller negative numbers (e.g., -0.1, -0.01, -0.001), 1/x gets larger and larger in the negative direction, approaching negative infinity.

  • The Limit Exists Only If: For the limit of 1/x as x approaches 0 to exist, both the limit from the right and the limit from the left must exist and be equal. Since they are not equal (+∞ vs -∞), the general limit lim (x→0) 1/x does not exist. We often say it is "undefined," or that it "diverges."

In summary:

While the expression 1/0 itself is undefined, in the context of limits, 1/x can approach positive or negative infinity as x approaches 0 from the right or left, respectively. Because these limits are not equal, the limit of 1/x as x approaches 0 does not exist.

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