[SomeCallMeTim?]

Originally Posted by 6Strings21Frets

I found something kinda funny about math here:

Theorem: 3=4
Proof:

Suppose:
a + b = c

This can also be written as:
4a - 3a + 4b - 3b = 4c - 3c

After reorganizing:
4a + 4b - 4c = 3a + 3b - 3c

Take the constants out of the brackets:
4 * (a+b-c) = 3 * (a+b-c)

Remove the same term left and right:
4 = 3

Fair enough!

You can do a lot of neat things if you ignore the fact that you are dividing by zero.
if a + b = c
then a + b - c = 0
and to get to the last line from the one before it, you must divide both sides by zero.
Since that isn't allowed, the proof is flawed.
Algebra is great!

[6strings21frets]

Originally Posted by SomeCallMeTim?

You can do a lot of neat things if you ignore the fact that you are dividing by zero.
if a + b = c
then a + b - c = 0
and to get to the last line from the one before it, you must divide both sides by zero.
Since that isn't allowed, the proof is flawed.
Algebra is great!

I don't really understand... can you show me where i divide by 0?
besides, you divide each side by (a+b-c) don't you?

[JerRocks2day]

Okay. Since this is an Algebra thread. I need some help with some math problems for tomorrows quiz. Here's the following:

• x+6=3(5-x)
• x+3/2 = 3/4(x-1/2)
• 27 - 2x = 2(x+1)
• x+4 = 2x-8(1/4x-1/4)

[Wesley7777]

1) 9/4
2) -15/2
3) 25/4
4) -2

[scared2mosh]

I cant understand this... what is the formula for finding a 5 digit non repeating number?
example
using 0-9 there are 100,000 posibilities for a 5 digit number. however when there are no repeating numbers there are 30,240 posibilties for a 5 digit number.

how do you find that answer?

the second problem is finding how many 5 digit numbers there are using only even numbers. the answer is 3125 but I dont know how to get that answer.

help?

thanks alot S2M

[JerRocks2day]

I need help with these:

Solve the system using the linear combination method. Then check your solution.

14) 3x-y=4
2x+3y=32

15. 4x-3y =10
x-2y=-14

16) 2x+2y=-16
2x+3y=-3

[SccHarpGirl]

Originally Posted by scared2mosh

I cant understand this... what is the formula for finding a 5 digit non repeating number?
example
using 0-9 there are 100,000 posibilities for a 5 digit number. however when there are no repeating numbers there are 30,240 posibilties for a 5 digit number.

how do you find that answer?

the second problem is finding how many 5 digit numbers there are using only even numbers. the answer is 3125 but I dont know how to get that answer.

help?

thanks alot S2M

To find a 5 digit non repeating number you should use the counting formula:

There are 10 possible digits that can go in space 1 (0 through 9). After you've put a number in there, that leaves 9 possibilities for space 2, then 8 for space 3, 7 for space 4, and 6 for space 5.

10*9*8*7*6 = 30,240.

Similarly if you could zero, there are 5 possible values for even digits (0, 2,4,6,and 8). Allowing for repetition, the answer is 5*5*5*5*5 = 3125.

I would argue that both of these answers are flawed because they allow for the possibility of the leading digit (the ten thousands digit) to be zero, in which case you would have a four digit, not a five digit number. but that's a small point...

Originally Posted by JerRocks2day

Solve the system using the linear combination method. Then check your solution.

14) 3x-y=4
2x+3y=32

15. 4x-3y =10
x-2y=-14

16) 2x+2y=-16
2x+3y=-3

14:
3x-y=4
2x+3y=32

Let's multiply equation 1 by 3
9x-3y=12
2x+3y=32

and add them together

11x=44
x=4
plugging into equation 1:
12-y=4
y=8

15.
4x-3y=10
x-2y=-14

Let's multiply equation 2 by -4

4x-3y=10
-4x+8y=56

and add them together

5y=66
y=13.2

by pluggin into equation 2 (can use either one, this one is just simpler
x =12.4

Try to do the 3rd one like these two (hope my numbers are OK - I did this on my weird computer calculator)

~noelle

[scared2mosh]

thanks

[the river stone]

i like algebra, why am i saying that when i have a d in that class? i don't know, but if you take your time, you will find out that algbra is easy.

[Ak_Man4Jesus]

I hate it. I had got steady Ds all year.