# Hello guys I need some help! :(

• Jun 3rd 2012, 08:30 PM
sambo
Hello guys I need some help! :(
Well first I'd like to say that I'm happy to meet you all! My friends told me you guys here are some of the smartest there is so I've decided to ask for some help here!

Here's my 1st question:

The typical planetary orbit can be modeled by an ellipse with the start at one focucs.
Suppose that two planets revolve around the same star.
How many possible points of intersection could there be?

a)0 or 1
b)0,1,or 2
c)0,1,2,or 4
d)0,1,2,3,or 4
I think its A. What do you guys say?

2nd question

Solve by using elimination:
4x2+9y2=36
4x2-25y2=100

a) (3,0) (-3,0)
b) no solution
c) (0, 32/17) (0,-32/17)
d) (3,32/17) (3,-32/17), (-3,32/17) , (-3,-32/17)
I said it was b. Thoughts?

Lastly:
Solve by using elimination or substitution:
x2+4y2=7
2y2-x=4

a) (-1,√6/2)
b) (0,√2), (0,-√2)
c) (1,±√10/2)
d) (-1,√6/2) (-1, -√6/2)
I said it c. Thoughts?

My test is tomorrow morning so if anyone could help me? I'd be more than thankful! Thanks.

PS: ± = plus or minus
√ = square root.... so √10/2 means the square root of 10 over 2.
• Jun 3rd 2012, 09:16 PM
Wilmer
Re: Hello guys I need some help! :(
Quote:

Originally Posted by sambo
1st question
I think its A. What do you guys say?

2nd question
I said it was b. Thoughts?

Lastly:
I said it c. Thoughts?

Sorry, but guesses are not part of maths.
You show no actual work...so we can't tell where you're stuck.
• Jun 4th 2012, 03:22 AM
sambo
Re: Hello guys I need some help! :(
This was no guess. I already worked it out and those are the answers I arrived at. Someone please tell me the correct answers.
• Jun 4th 2012, 05:47 AM
Reckoner
Re: Hello guys I need some help! :(
Quote:

Originally Posted by sambo
This was no guess. I already worked it out and those are the answers I arrived at.

How are we supposed to know that? Nothing you wrote in your post indicates that you put any effort into these problems. Why don't you show us what you've done, and then we can tell you if you are on the right track?