Solutions - Introduction to Mathematical Methods for...

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Introduction to Mathematical Methods for Economics and Management, 2003 Week 1 Solutions to Worksheet 1 Review of Algebra Question 4. Simplify: (a) 6 a 4 b × 4 b ÷ 8 ab 3 c Solution: 6 a 4 b × 4 b ÷ 8 ab 3 c = 3 a 3 bc (b) p 3 x 3 y ÷ 27 xy Solution: p 3 x 3 y ÷ 27 xy = x 3 (c) ¡ 2 x 3 ¢ 3 × ¡ xz 2 ¢ 4 Solution: ¡ 2 x 3 ¢ 3 × ¡ xz 2 ¢ 4 =8 x 13 z 8 Question 8. Write as a single logarithm: (a) 2log a (3 x )+log a x 2 Solution: a (3 x a x 2 =log a ¡ 9 x 4 ¢ (b) log a y 3log a z Solution: log a y a z a ¡ y z 3 ¢ Question 9. Solve the following equations: (a) 5(2 x 9) = 2 (5 3 x ) Solution: x 9) = 2 (5 3 x ) ,So lut ionis : x = 55 16 (b) 1+ 6 y 8 = 1 Solution: 6 y 8 = 1 : y =5 (c) z 0 . 4 =7 Solution: z 0 . 4 : z 5 2 = 129 . 64 (d) 3 2 t 1 =4 Solution: 3 2 t 1 : t = (ln3+ln4) 2ln3 =1 . 130 9 Question 10. Solve these equations for x, in terms of the parameter a : (a) ax 7 a Solution: ax 7 a : x = ½ © 1 a (7 a +1) ª if a 6 =0 if a (b) 5 x a = x a 1
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Solution: 5 x a = x a ,So lut ionis : x = ( n a 1 a +5 o if a 6 = 1 5 if a = 1 5 (c) log a (2 x +5)=2 Solution: log a (2 x : x = 1 2 a 2 5 2 Question 11. Make Q the subject of: P = q a Q 2 + b Solution: P = q a Q 2 + b >Q = p a P 2 b Question 12. Solve the equations: (a) 7 2 x 2 =5 x Solution: 7 2 x 2 x : x = 7 2 , 1 (b) y 2 +3 y 0 . 5=0 Solution: y 2 y 0 . : y = 3 . 158 3 , 0 . 158 31 (c) | 1 z | Solution: | 1 z | : z = 4 , 6 Question 13. Solve the simultaneous equations: (a) 2 x y =4 and 5 x y +13 Solution: 2 x y 5 x y : [ x =1 ,y = 2] (b) y = x 2 +1 and 2 y =3 x +4 Solution: y = x 2 2 y x : [ x =2 =5] , £ x = 1 2 = 5 4 ¤ Question 14. Solve the inequalities: (a) 2 y 7 3 Solution: 2 y 7 3 : y ( −∞ , 5] (b) 3 z> 4+2 z Solution: 3 z : z ¡ −∞ , 1 3 ¢ (c) 3 x 2 < 5 x +2 Solution: 3 x 2 < 5 x : x ¡ 1 3 , 2 ¢ Solutions to Worksheet 2 Lines and Graphs Question 6. 2
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Sketch the graph of y =3 x x 2 +4 , and hence solve the inequality 3 x x 2 < 4 . Solution: y ( x )=3 x x 2 y ( x ) 5 2.5 0 -2.5 -5 0 -10 -20 -30 x y 3 x x 2 < 4 ,So lut ionis : x ( −∞ , 1) (4 , ) Question 7. Draw a diagram to represent the inequality 3 x 2 y< 6 . Solution: 3 x 2 6 or y> 3 2 x 3 First let us sketch the graph y ( x )= 3 2 x 3 y ( x ) 5 2.5 0 -2.5 -5 2.5 0 -2.5 -5 -7.5 -10 x y Theareaabovethestra ightl ine y ( x 3 2 x 3 represents the inequality in question. Question 8. 3
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Electricity costs 8p per unit during the daytime and 2p per unit if used at night. The quarterly charge is £10. A consumer has £50 to spend on electricity for the quarter. (a) What is his budget constraint? Solution: 8Day+2N ight 4000 or 4Day+N 2000 (b) Draw his budget set (with daytime units as "good 1" on the horizontal axis). Solution: Re-write 2000 as 4 x + y 2000 Hence the budget line is given by y ( x ) = 2000 4 x y ( x ) 500 375 250 125 0 2000 1500 1000 500 0 x y (c) Is the bundle (440 , 250) in his budget set? Solution: No, as the bundle costs 4020 (d) What is the gradient of the budget line?
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This note was uploaded on 04/12/2010 for the course ECON DEAM taught by Professor Vines during the Spring '10 term at Oxford University.

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Solutions - Introduction to Mathematical Methods for...

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