11.7+OFSA+Solutions


 * OFSA SOLUTIONS for Conics A (Full)**

This page contains peer generated solutions and error explanations to OFSA questions. As you read or view the solutions, be critical: check for accuracy, but also for more efficient solution strategies. If you have a better method or different idea/answer, post a discussion and monitor the responses.


 * Quick Directions**
 * Post answers, solutions and error explanations to each OFSA question below.
 * For each "distractor" or incorrect answer choice, explain the error that would lead to that incorrect answer choice.
 * You may either do the above in typed format or using a pencast.
 * Separate each question with a section bar.
 * After each solution, provide a hyperlink back to the corresponding OFSA page.
 * Follow example below.
 * Click here to refer to solution format in 7.7

b. is correct because the a term is with the x and the b term is with the y. Also there is a negative and the equation is equal to 1. a. is wrong because the a and b terms are switched. c. is wrong because it has a plus instead of a minus. It is the general equation of an ellipse. d. is wrong because it has no a or b term at all. It would be the equation of a circle if the minus was a plus. Click here to return to OFSA.
 * Question 1**
 * __Solution 1__**
 * __Error Explanation 1__**

c. is correct because the plus indicates an ellipse and it has the correct center at (0,4). The c value can be found from distance between the foci divided by 2 and then using the eccentricity to find a as 6. Then using the relationship math a^{2}-b^{2}=c^{2} math we find b as math \sqrt{27} math a. is wrong because the a and b terms are not squared. b. is wrong because the center of the ellipse is incorrectly identified as (3,-4). d. is wrong because it is the equation of a hyperbola. Click here to return to OFSA.
 * Question 2**
 * __Solution 2__**
 * __Error Explanation 2__**

a. is correct because it is 2 left of the vertex. The value of p can be found from the focal diameter = 4p. The focus is on the axis of symmetry a distance p away from the vertex in the dircetion that the parabola opens. b. is wrong because it is in the opposite direction. c. is wrong because it is too far. The point is 2p away from the vertex. d. is wrong because it is a distance p up, not to the left. Click here to return to OFSA.
 * Question 3**
 * __Solution 3__**
 * __Error Explanation 3__**

a. is correct because if you complete the square you get the equation of the conic b. is wrong because the end term must be 81 since 68+4+9 = 81 c. is wrong because the square was completed incorrectly and the radius is said to be 1 d. is wrong because the square was completed incorrectly Click here to return to OFSA.
 * Question 4**
 * __Solution 4__**
 * __Error Explanation 4__**

b. is correct because the value under x should be 25 and the value under y should be 4. a. is wrong because the hyperbola opens north/south when it should open east/west c. is wrong because the 4 should be under y and the 25 should be under x also that hyperbola opens n/s instead of e/w d. is wrong because the 4 should be under y and the 25 should be under x Click here to return to OFSA.
 * Question 5**
 * __Solution 5__**
 * __Error Explanation 5__**

d. is correct because an ellipse is x+y and the values below the x and y should be 16 and 9 respectively a. is wrong because the a and b values aren't squared b. is wrong because it is x-y and that is for hyperbolas also the a and b values need to be squared. c. is wrong because x-y is for hyperbolas Click here to return to OFSA.
 * Question 6**
 * __Solution 6__**
 * __Error Explanation 6__**

It opens right. The equation is an x hyperbola, and since the negative is outside the square root, only the left side of the graph is drawn.
 * Question 7**
 * Which way does the equation x=-4sqrt(9+y^2) open?**
 * __Solution 7__**
 * __Error Explanation 7__**

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 * Question 8**
 * __Solution 8__**
 * __Error Explanation 8__**

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 * Question 9**
 * __Solution 9__**
 * __Error Explanation 9__**

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 * Question 10**
 * __Solution 10__**
 * __Error Explanation 10__**

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 * Question 11**
 * __Solution 11__**
 * __Error Explanation 11__**

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 * Question 12**
 * __Solution 12__**
 * __Error Explanation 12__**

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 * Question 13**
 * __Solution 13__**
 * __Error Explanation 13__**

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 * Question 14**
 * __Solution 14__**
 * __Error Explanation 14__**

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 * Question 15**
 * __Solution 15__**
 * __Error Explanation 15__**

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 * Question 16**
 * __Solution 16__**
 * __Error Explanation 16__**

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 * Question 17**
 * __Solution 17__**
 * __Error Explanation 17__**

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 * Question 18**
 * __Solution 18__**
 * __Error Explanation 18__**

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 * Question 19**
 * __Solution 19__**
 * __Error Explanation 19__**

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 * Question 20**
 * __Solution 20__**
 * __Error Explanation 20__**

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 * Question 21**
 * __Solution 21__**
 * __Error Explanation 21__**

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 * Question 22**
 * __Solution 22__**
 * __Error Explanation 22__**

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 * Question 23**
 * __Solution 23__**
 * __Error Explanation 23__**

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 * Question 24**
 * __Solution 24__**
 * __Error Explanation 24__**