(1) Evaluate the following limits. State the asymptotes, if any: (i) \( \lim _{t \rightarrow 3} \frac{2-t}{-2 t^{2}+7 t-3} \) (ii) \( \lim _{x \rightarrow-\infty} \frac{x-\sqrt{x^{2}-x+1}}{2 x-\sqrt{4 x^{2}+5 x-1}} \)
Real Tutor Solution
Answer
Solution
Reviewed and approved by the UpStudy tutoring team
Mind Expander
Let's evaluate the limits step by step, starting with the first one. (i) To find the limit \( \lim _{t \rightarrow 3} \frac{2-t}{-2t^{2}+7t-3} \), we first substitute \( t = 3 \) into the denominator: \[ -2(3^2) + 7(3) - 3 = -18 + 21 - 3 = 0. \] This gives us a \( 0 \) in the denominator. We then need to factor the denominator. The polynomial \( -2t^2 + 7t - 3 \) can be factored as follows: \[ -2t^2 + 7t - 3 = -(2t^2 - 7t + 3) = -(2t - 1)(t - 3). \] Thus, the limit can be rewritten as: \[ \lim_{t \rightarrow 3} \frac{2-t}{-(2t-1)(t-3)}. \] We can now cancel \( t - 3 \) in the numerator and denominator (noting that we are approaching \( t = 3 \), so we are not actually at 3): \[ = \lim_{t \rightarrow 3} \frac{2-t}{-(2t-1)} = \lim_{t \rightarrow 3} \frac{-(t-2)}{-(2t-1)} = \lim_{t \rightarrow 3} \frac{t-2}{2t-1}. \] Substituting \( t = 3 \): \[ = \frac{3-2}{2(3)-1} = \frac{1}{6-1} = \frac{1}{5}. \] Thus, the limit is \( \frac{1}{5} \) and we note that there is a vertical asymptote at \( t = 3 \) since the denominator equals zero there. (ii) Now we evaluate \( \lim _{x \rightarrow-\infty} \frac{x-\sqrt{x^{2}-x+1}}{2x-\sqrt{4x^{2}+5x-1}} \). To simplify for large negative \( x \), we factor out \( x \) from the square roots in both the numerator and denominator. In the numerator: \[ \sqrt{x^2 - x + 1} = \sqrt{x^2(1 - \frac{1}{x} + \frac{1}{x^2})} = |x| \sqrt{1 - \frac{1}{x} + \frac{1}{x^2}} = -x\sqrt{1 - \frac{1}{x} + \frac{1}{x^2}} \text{ (as \( x \to -\infty \))}. \] Thus, we rewrite the numerator: \[ x - \sqrt{x^2 - x + 1} = x + x\sqrt{1 - \frac{1}{x} + \frac{1}{x^2}} = x(1 + \sqrt{1 - \frac{1}{x} + \frac{1}{x^2}}). \] In the denominator: \[ \sqrt{4x^2 + 5x - 1} = |2x|\sqrt{1 + \frac{5}{4x} - \frac{1}{4x^2}} = -2x \sqrt{1 + \frac{5}{4x} - \frac{1}{4x^2}}. \] Thus, the denominator becomes: \[ 2x - \sqrt{4x^2 + 5x - 1} = 2x + 2x\sqrt{1 + \frac{5}{4x} - \frac{1}{4x^2}} = 2x(1 + \sqrt{1 + \frac{5}{4x} - \frac{1}{4x^2}}). \] Now we can simplify the limit: \[ \lim_{x \rightarrow -\infty} \frac{x(1 + \sqrt{1 - \frac{1}{x} + \frac{1}{x^2}})}{2x(1 + \sqrt{1 + \frac{5}{4x} - \frac{1}{4x^2}})} = \lim_{x \rightarrow -\infty} \frac{1 + \sqrt{1 - \frac{1}{x} + \frac{1}{x^2}}}{2(1 + \sqrt{1 + \frac{5}{4x} - \