s251ex1(su07)

s251ex1(su07) - 6 cos 3 3 2 2-=-+ x y x y x 9. y ( t ) = 2...

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MATH 251 Exam 1 July 9, 2007 ANSWER KEY 1. C, E, H, D, A 2, B 3. C 4. A 5. A 6. D 7. (a), (b) The 3 equilibrium solutions are: y = -1 (stable), y = 0 (unstable), and y = 2 (stable). (c) y = 0 (d) 1 ) ( lim - = t y t (e) 0 < α < . 8. (a) x N y xy y M = - = sin 12 (b)
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Unformatted text preview: 6 cos 3 3 2 2-=-+ x y x y x 9. y ( t ) = 2 + ln t 10. 2 2 2 sin 2 cos ) ( 2 2 1-+ + + = t t t e C t e C t y t t . 11. (a) 20 Q dt dQ-= , or 20 = + Q dt dQ ; Q (0) = 120, (b) 20 / 120 ) ( t e t Q-= (c) 20 ln(10)...
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