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Evaluating a limit by factoring to remove a 0/0 form

Consider the function a(x)=x2+3x−10x−2.a(x) = \frac{x^2 + 3x - 10}{x-2}. Note that direct substitution of x=2x=2 gives the indeterminate form 0/00/0. Factor the numerator, cancel the common factor with the denominator, and then use the limit laws to evaluate lim⁡x→2a(x).\lim_{x \to 2} a(x).

Hint

Factor x2+3x−10x^2 + 3x - 10 into two binomials. One of them should match the denominator, allowing you to simplify the expression before substituting x=2x = 2.

Step-by-step solution

Since substituting x=2x=2 directly gives 4+6−100=00\frac{4+6-10}{0} = \frac{0}{0}, an algebraic simplification is needed. Factor the numerator: x2+3x−10=(x−2)(x+5)x^2 + 3x - 10 = (x-2)(x+5). This shows the numerator and denominator share a common factor of (x−2)(x-2).

For x≠2x \neq 2, we can cancel the common factor to write a(x)=x+5a(x) = x+5. Since this simplified expression is a polynomial (continuous everywhere), the quotient and sum rules justify evaluating the limit by direct substitution: lim⁡x→2(x+5)=2+5=7\lim_{x\to 2}(x+5) = 2+5 = 7.

Identifying the simplified linear expression after cancellation

Hint
Step-by-step solution

After factoring the numerator and canceling the common factor of x minus two, the expression simplified to x plus five. This linear expression is continuous everywhere, so direct substitution of x equals two could then be applied. The cancellation step is what removed the original zero over zero indeterminate form.

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