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Answers for “为什么简化后的函数在目标点附近与原函数一致?”

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Factoring and cancelling resolves the limit by simplifying the expression to a form that is defined near the target point. For x≠2x \ne 2 near 2, the expression x2+3x−10x2−2x\frac{x^2+3x-10}{x^2-2x} factors into (x−2)(x+5)x(x−2)\frac{(x-2)(x+5)}{x(x-2)}.

Conditions: The limit is as x→2x \to 2.; The original expression is undefined at x=2x=2 (indeterminate form 0/00/0).; Cancellation is valid only for x≠2x \ne 2.

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The simplified functions agree with the original expressions near the target point because the algebraic manipulations (factoring, conjugate multiplication, clearing fractions) are equivalences valid for all xx in the domain except possibly the target point itself. Limits describe the behavior of a function as the input approaches a value, not the value of the function at that point.

Conditions: The target point is excluded from the domain of the original expression.; The algebraic simplification is valid for all xx near the target point (x≠x \ne target).; The limit exists for the simplified function.