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Lecture Notes Limits at In nity - Part 1 page 1 Sample Problems 1. Compute each of the following limits. a) lim 3x4 c) lim ( 2x5) e) lim 2x6 g) lim 4x3 x!1 x!1 x!1 3 x!1 4 5 2 6 3 b) lim 3x d) lim ( 2x ) f) lim x h) lim 4x x! 1 x! 1 x! 1 3 x! 1 2. Compute each of the following limits. a) lim 1 d) lim 5 7+ 8 g) lim 5x3 2x+4 x!1x x! 1 2x3 x x!1 x2 b) lim 1 e) lim 2x3 +1 5 + 12 h) lim 5x3 2x+4 x! 1x x!1 x x4 x!1 x3 5 3x 2 5x3 2x+4 c) lim 3 f) lim i) lim 4 x!12x x! 1 x x!1 x 3. Compute each of the following limits. a) lim ( 2x5 8x4 +7x3 10) c) lim ( 2x5 +8x6) x! 1 x! 1 b) lim ( 2x5 8x4 +7x3 10) d) lim ( 2x5 +8x6) x!1 x!1 4. Compute each of the following limits. x+x2 6 x2 +9 x3 9x+1 a) lim 2 3 b) lim 2 c) lim 2 x! 16x+5x +2x x!15x+2x 3 x! 13x 2x 15 Practice Problems 1. Compute each of the following limits. a) lim 3x15 c) lim 1x8 e) lim 4x9 g) lim ( 7x10) x!1 8 x!13 x!1 x!1 b) lim 3x15 d) lim 1x8 f) lim 4x9 h) lim ( 7x10) x! 1 8 x! 13 x! 1 x! 1 c copyright Hidegkuti, Powell, 2009 Last revised: May 21, 2011 Lecture Notes Limits at In nity - Part 1 page 2 2. Compute each of the following limits. a) lim 3 g) lim 5x 2 m) lim 3x5+2x 5 x!1x5 x!1 x+3 x!1 x2 b) lim 3 h) lim 5x 2 n) lim 3x5+2x 5 x! 1x5 x! 1 x+3 x! 1 x2 c) lim 1 2 + 5 i) lim 5x 3 o) lim 4x8 +x3 x+7 x!1 x 3x4 x!1 x x!1 x4 d) lim 1 2 + 5 j) lim 5x 3 p) lim 4x8+x3 x+7 x! 1 x 3x4 x! 1 x x! 1 x4 e) lim 3+ 5 7 k) lim 1 3x x!1 x3 6x x!1 2x f) lim 3+ 5 7 l) lim 1 3x x! 1 x3 6x x! 1 2x 3. Compute each of the following limits. 5 3 5 1 6 4 3 1 a) lim ( 7x +x ) c) lim 120x x e) lim 8x 3x x+2 x! 1 x! 1 4 x! 1 5 5 3 5 1 6 4 3 1 b) lim ( 7x +x ) d) lim 120x x f) lim 8x 3x x+2 x!1 x!1 4 x! 1 5 4. The graph of a polynomial function is shown on the picture below. What can we state about this polynomial based on its end-behavior? yy xx 5. Compute each of the following limits. a) lim 1 d) lim 3 2 + 11 g) lim 3x2 1 x! 1x x!1 x x4 x! 15x2 3x+2 5 2x2 +3x+1 20x 2x2 42 b) lim 3 e) lim 2 h) lim 3 2 x! 12x x!13x 5x+2 x! 15x 20x 105x 5 3x3+2x+1 c) lim 2 3 f) lim x! 1 x x! 1 5x 3 c copyright Hidegkuti, Powell, 2009 Last revised: May 21, 2011 Lecture Notes Limits at In nity - Part 1 page 3 Sample Problems - Answers 1. a) 1 b) 1 c) 1 d) 1 e) 1 f) 1 g) 1 h) 1 2. a) 0 b) 0 c) 0 d) 7 e) 1 f) 3 g) 1 h) 5 i) 0 3. a) 1 b) 1 c) 1 d) 1 4. a) 0 b) 1 c) 1 2 Practice Problems - Answers 1. a) 1 b) 1 c) 1 d) 1 e) 1 f) 1 g) 1 h) 1 2. a) 0 b) 0 c) 1 d) 1 e) 3 f) 3 g) 1 h) 1 i) 5 j) 5 k) 3 l) 3 2 2 m) 1 n) 1 o) 1 p) 1 3. a) 1 b) 1 c) 1 d) 1 e) 1 f) 1 4. Since lim f (x) = 1 and lim f (x) = 1, the polynomial is of odd degree and has a positive x! 1 x!1 leading coe¢ cient. 5. a) 0 b) 0 c) 2 d) 3 e) 2 f) 1 g) 3 h) 0 3 5 c copyright Hidegkuti, Powell, 2009 Last revised: May 21, 2011 Lecture Notes Limits at In nity - Part 1 page 4 Sample Problems - Solutions 1. Compute each of the following limits. a) lim 3x4 x!1 Solution: Since the limit we are asked for is as x approaches in nity, we should think of x as a very large positive number. Then 3x4 is very large, and also positive because it is the product of ve positive numbers. 3x4 = 3 x x x x positive positive positive positive positive So the answer is 1. We state the answer: lim 3x4 = 1. x!1 b) lim 3x4 x! 1 Solution: Since the limit we are asked for is as x approaches negative in nity, we should think of x as a very large negative number. Then 3x4 is very large, and also positive because it is the product of one positive and four negative numbers. 3x4 = 3 x x x x positive negative negative negative negative So the answer is 1. We state the answer: lim 3x4 = 1 x! 1 c) lim ( 2x5) x!1 Solution: Since the limit we are asked for is as x approaches in nity, we should think of x as a very large positive number. Then 2x5 is very large, and also negative because it is the product of one negative and ve positive numbers. 2x5 = 2 x x x x x negative positive positive positive positive positive So the answer is 1. We state the answer: lim ( 2x5) = 1 x!1 d) lim ( 2x5) x! 1 Solution: Since the limit we are asked for is as x approaches negative in nity, we should think of x as a very large negative number. Then 2x5 is very large, and also positive because it is the product of six negative numbers. 2x5 = 2 x x x x x negative negative negative negative negative negative So the answer is 1. We state the answer: lim ( 2x5) = 1 x! 1 c copyright Hidegkuti, Powell, 2009 Last revised: May 21, 2011
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