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Math Question

post #1 of 22
Thread Starter 
This should be easy but I can't figure out how to do it.

Find a function that connects the following points.

-4 to 9
-6 to 11
-8 to 13
-10 to 15
-12 to 17
-14 to 19

all the way to - infinity and positive infinity.
post #2 of 22
I'm not entirely sure what you mean but is it y=-(x-5)? If not ignore me.

Edit - Wait, if its a function then f(x)=-(x-5)?
post #3 of 22
Thread Starter 
thats what someone else I talked to came up with also so I am guessing its right but I'm not exactally sure why...I'm to tired to really care either.
post #4 of 22
13
17
21
25
29
31

looks like all primes to me.

Not sure if that is what you are looking for either.
post #5 of 22
what does the "to" mean?
post #6 of 22
I noticed there was a gap of 5 between the f(x) and x before I noticed the positive/negative signs, and to change a positive to a negative and vice versa just times it by -1.

The 'to' just separates the numbers into pairs. Connect A to B. I think.
post #7 of 22
Thread Starter 
yes you are right. To means connect.

Here is another one thats been bugging me all day.

Given two irrational numbers is there product also irrational. And if it is explain why. Its the explain why that is bugging me.
post #8 of 22
Thread Starter 
Quote:
Originally Posted by tierre0 View Post
13
17
21
25
29
31

looks like all primes to me.

Not sure if that is what you are looking for either.
21 and 25 are not primes though. The list of numbers on the right is all the odd numbers greater than or equal to 9 and the list of numbers on the left is all the numbers less than or equal to -4.
post #9 of 22
Sqrt 2 is irrational, but sqrt 2 x sqrt 2 = 2
post #10 of 22
Thread Starter 
wow your on a roll. Okay one more.

Let x y and z be real numbers with x < y. Is it true that xz < yz?
post #11 of 22
As much as I love math and all if this is for school/educational pruposes, just giving/getting the answers won't help you learn the why's of it.
post #12 of 22
For the first question you posted. Get a piece of graph paper and draw your x and y axis, then plot each point on the graph paper. The points will plot a line. Using the slope of the line (dy/dx) and the x-intercept, you can get the formula for that line.

As for the last question, if x, y, and z are reals, and the statement x < y, x*z < y*z is true if and only if z is positive.

Just take the original formula "x<y", and multiply both sides by z,

if z is zero, then both sides equal zero,

if z is negative, and both x and y are positive, since y would be the greater negative, y would be less than x.

if z is negative, and If x is negative and y is positive then x becomes positive and y becomes negative making y < x.

In the expression there can't be a case where y is negative and x is positive, since that would make the "x < y" statement false.

There's also the cases for negative z where either x or y is zero (and the other number is either positive or negative, which ever makes the original statement true), but I'm sure you'd be smart enough to know what happens in those two.
post #13 of 22
Thats what I would have said if it wasn't midnight my time when you posted the question.

Just out of curiosity, how old are you/ what level maths are you studying Algebrapro?

My bf started his degree in Maths at UCL today, and was asked a couple of maths questions so I'll post one for fun and to see if anyone can answer it.

What set of consecutive numbers add up to exactly 2000?
post #14 of 22
Thread Starter 
I am 23 and in my 5th year as a math major and this is a senior level class. Its basically a calculus proofs course but we haven't started calculus proofs yet were just doing a lot of the preliminary stuff at the moment.
post #15 of 22
Quote:
Originally Posted by cata_mint View Post
Thats what I would have said if it wasn't midnight my time when you posted the question.

Just out of curiosity, how old are you/ what level maths are you studying Algebrapro?

My bf started his degree in Maths at UCL today, and was asked a couple of maths questions so I'll post one for fun and to see if anyone can answer it.

What set of consecutive numbers add up to exactly 2000?
499, 500, 501

ETA: OMG, sleepytime? That's 1500. lol

ETA again... 398, 399, 400, 401, 402
post #16 of 22
That's right!

How about... You have a quantity of eggs. How many eggs do you need to be able to share them equally between 2, 3, 4, 5 and 6 people while always having 1 egg remaining?


Algebrapro, your lecturers must be nicer than my bf's, his seem to be doing their best to get the students to fail. They write up equations and say 'if you cannot understand this equation by the end of the year then you have no business studying this subject'. And make jokes about the poor quality of the students. I think my bf is enjoying the challenge though
post #17 of 22
Is it 721? These are fun
post #18 of 22
You can do it with fewer eggs than that.
I'm glad you like them, I might ask him to tell me a few more.
post #19 of 22
Quote:
Originally Posted by cata_mint View Post
You can do it with fewer eggs than that.
I'm glad you like them, I might ask him to tell me a few more.
Is it 181 then?
post #20 of 22
Quote:
Originally Posted by Going Nova View Post
Is it 181 then?
Its even less than that! I'm impressed that you've managed 2 though, I basically gave up after realising that 20 and 30 wouldn't work
post #21 of 22
61????



post #22 of 22
Yes!
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