# Thread: Eqn. of a line

1. ## Eqn. of a line

The equation of the line goes through the points (-4, 7) and (4, -7)
what is the slope?
What is the B value?

I keep getting 3/4, which is incorrect.?

2. Originally Posted by B-lap
The equation of the line goes through the points (-4, 7) and (4, -7)
what is the slope?
What is the B value?

I keep getting 3/4, which is incorrect.?
The equation of a slop is $m=\frac{y_2-y_1}{x_2-x_1}$

Then you can stick this into the equation $y-y_1=m(x-x_1)$

and then put it into slope intercept form $y=mx+b$

3. Erm, hai...for what I can see is that you just need to find the slope using the general equation, which is y2 - y1 / X2 - X1...

And you will get (-14/8),
then you just use slope equation to find for the equation of line...

You should get these, y= -7/4...and I think it should not be 3/4
Aright then, best regards and work hard yeah..me too, haha..

4. $(-4, 7),(4, -7)$

$\frac{y - y_1}{y_2 - y_1} = \frac{x - x_1}{x_2 - x_1}$

$\frac{y - 7}{-7 - 7} = \frac{x - (-4)}{4 - (-4)}$

$\frac{y - 7}{-14} = \frac{x + 4}{8}$

$8(y - 7) = -14(x + 4)$

$8y - 56 = -14x - 56$

$8y = -14x$

$y = \frac{-14}{8}x + 0$

The gradient (m) is $\frac{-14}{8}$ and the y-intercept (c or b) is 0.

5. Originally Posted by B-lap
I keep getting 3/4, which is incorrect.?
If you show your steps, then we'd be able to help you find the error, so you won't make the same mistake in the future.