algebra solve help

• Apr 15th 2007, 09:28 AM
Patience
algebra solve help
1. Solve the system by addition.
4x – 7y = 17
x – 5y = 1

2. Find the slope of the line passing through the points (–1, 1) and (–2, 9).

m= y/x = 9-1/-2-(-1)= -8
So slope is -8.
• Apr 15th 2007, 09:35 AM
mbaboy
Quote:

Originally Posted by Patience
1. Solve the system by addition.
4x – 7y = 17
x – 5y = 1

2. Find the slope of the line passing through the points (–1, 1) and (–2, 9).

m= y/x = 9-1/-2-(-1)= -8
So slope is -8.

For #1 multiply the second equation by -4 so for both equations become:

4x - 7y = 17
-4x + 20y = -4

Then add then together and the x's cancel out:

13y = 13

So y=1 and x would then equal 6.

• Apr 15th 2007, 11:06 AM
topsquark
Quote:

Originally Posted by Patience
2. Find the slope of the line passing through the points (–1, 1) and (–2, 9).

m= y/x = 9-1/-2-(-1)= -8
So slope is -8.

I agree with mbaboy, this answer is correct. But the way you wrote it is horrible! You really must use parentheses because
9-1/-2-(-1) = 9 + 1/2 + 1 = 10 + 1/2 = 21/2

You need to write this as:
[9-1]/[-2-(-1)]
or some such.

Also your slope formula is written incorrectly. It should be:
m = (y2 - y1)/(x2 - x1)
where your points are (x1, y1) and (x2, y2).

It may seem like I'm picking at trivial things, but I'm really not. After all, if you don't communicate clearly others won't be able to understand you.

-Dan
• Apr 15th 2007, 11:13 AM
Jhevon
Quote:

Originally Posted by topsquark

It may seem like I'm picking at trivial things, but I'm really not. After all, if you don't communicate clearly others won't be able to understand you.

-Dan

I agree with topsquark, and it's not picking at trivial things, these things can come back to haunt you on tests. you write the thing without the proper parenthesis even though you know what the correct answer should be. then the examiner says "ok, 5 mins left" you start to panick, forgetting where the parenthesis should be, and boom, wrong answer