Engineering Board Exam Reviewer · Ellipses · medium
Find the foci of the ellipse (x-2)2/25+(y+1)2/9=1.
- (2,3) and (2,-5)
- (7,-1) and (-3,-1)
- (6,1) and (-2,1)
- (6,-1) and (-2,-1)
Answer
D. (6,-1) and (-2,-1)
Solution
The center is (2,-1), a=5, b=3, so c=sqrt(25-9)=4. The major axis is horizontal, so the foci are (2 4,-1), i.e. (6,-1) and (-2,-1).
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