Exam2_2 8 - storm is given by s t = 4-2 t the negative sign...

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Taylor, Douglas – Exam 2 – Due: Oct 31 2007, 1:00 am – Inst: JEGilbert 8 eliminating a third answer. Hence one of f ( x ) = x 2 + 3 x - 8 x 2 - 9 or f ( x ) = x 2 - 3 x + 8 x 2 - 9 or f ( x ) = x 2 + 3 x + 8 x 2 - 9 must hold. But the y -intercept of the graph is positive, while the y -intercepts of these possi- ble f are f (0) = 8 9 , or - 8 9 and only one has the property f (0) = 8 9 . Con- sequently, f ( x ) = x 2 + 3 x - 8 x 2 - 9 . keywords: graph, rational function, vertical asymptote, horizontal asymptote 016 (part 1 of 1) 10 points A storm system is headed towards Austin. The Weather Service OFce forecasts that t hours after mid-day the storm will be at a distance of s ( t ) = 5 + 4 t - t 2 miles from Austin. At what speed (in miles per hour) will the storm be moving when it reaches Austin? 1. storm speed = - 7 mph 2. storm speed = - 6 mph 3. storm speed = 8 mph 4. storm speed = 6 mph correct 5. storm speed = 7 mph 6. storm speed = - 8 mph Explanation: The storm will reach Austin when s ( t ) = (5 - t )(1 + t ) = 0 , i.e. , when t = 5. Now the velocity of the
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Unformatted text preview: storm is given by s ( t ) = 4-2 t, the negative sign indicating that the storm is moving towards Austin. Thus at t = 5, s ‡ 5 · = 4-10 =-6 . Consequently, since speed is always non-negative, storm speed = 6 mph . keywords: instantaneous speed, derivative 017 (part 1 of 1) 10 points The cost function for Levi Strauss to pro-duce x pairs of blue jeans is C ( x ) = 5000 + 5 x-3 100 x 2 + 7 10000 x 3 . ±ind the marginal cost to Levi Strauss of producing 100 pairs of blue jeans. 1. marginal cost = $18 per pair 2. marginal cost = $19 per pair 3. marginal cost = $16 per pair 4. marginal cost = $20 per pair correct 5. marginal cost = $17 per pair Explanation: By de²nition, the Marginal cost is the derivative, C ( x ), of the cost function C ( x ). Now C ( x ) = 5-3 50 x + 21 10000 x 2 ....
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