+34 One more for all of you that are smarter than me, and I'm not being sarcastic. I picked the correct graph, but got the foci point backwards. I don't understand how though. I'd appreciate it if someone could give me a step-by-step insight into what I did wrong. The answer I got was (2√4,0), (-2√4,0). The program says that the correct answer is (0,2√4),(0,-2√4). Could someone show me where I went wrong?
+34 Sorry about that. I'm trying to work as a line mechanic while doing this homework quiz and forgot to put it in. The original problem is: 81x²+25y²=2025.
I get the 81x²/2025+25y²/2025=2025/2025 is x²/25+y²/81=1, the I s***w up. I've got the vertices at (0,9),(0,-9) for the major axis and (5,0),(-5,0) for the minor axis. I thought I had the foci correct with c²=a²-b²: c²=81-25=56; c²=56; c=√56. It's here I screwed up, I think. I don't remember when to put the 2√4 in the x or y position.
+128406 81x²+25y²=2025 → standard form is :
x^2 / 25 + y^2 / 81 = 1
The center is (0, 0) the major axis is along y
So......tthe focal points are (0, 0 ±√ [ 81 - 25] ) = (0, ±√ 56) = (0 , ± 2√14 )
Remember....once we get the equation in standard form....the major axis will always lie along whichever number is larger under either x or y terms...here....81 > 25 so the major axis lies along y [ this is where you probably made a mistake]
+34 I think I figured it out. I forgot that the major axis is vertical, with the y-axis at (0). Sorry, I was overthinking it.
+34 It's supposed to say (your) and f a r t. I can't believe they censored that. Anyway CPhill, this old coot thanks you for your help. I do have one more question. How do you know when to put the points as (-#,0),(#,0) vs. (#,0),(-#,0)? While I got the answer right, (2√6/5,0),(-2√6/5), the test said I got it wrong because I didn't put it as (-2√6/5,0), (2√6/5,0). What difference does it make which order the pairs are as long as they are correct?
