# Thread: Finding the slope of a line

1. ## Finding the slope of a line

We just started doing inequalities in class and I get the basics, but this is what gets me.

M = 7, point (0,-5)

How would I write this in Y = mx + b format?

2. $\displaystyle y = m * x + b$
First, we know m:

$\displaystyle y = 7 * x + b$

Next, we know x and y:

$\displaystyle -5 = 7 * 0 + b$

Solve for b:

$\displaystyle -5 = b$

Notice, if $\displaystyle x = 0$, and $\displaystyle (x,y)$ is on the line, $\displaystyle b = y$.

So, now, write your equation down:

$\displaystyle y = 7 * x + -5$

Or:

$\displaystyle y = 7 * x - 5$

3. Originally Posted by largebabies
We just started doing inequalities in class and I get the basics, but this is what gets me.

M = 7, point (0,-5)

How would I write this in Y = mx + b format?
The y intercept = -5, therefore

y=7x-5

4. m=7, (0,-5)

y- (-5)
_______ = 7 : then cross multiply
x-0

y+5= 7x: move five to the other side by subtracting it

so then you get y=7x -5

5. Thank you all, it's help alot

Although, I need help on another equation, what if there is two points?

example: M = 3/2, point (5,-6)?

6. $\displaystyle y = m * x + b$
First, we know m:

$\displaystyle y = \frac 3 2 * x + b$

Next, we know x and y:

$\displaystyle -6 = \frac 3 2 * 5 + b$

Solve for b:

$\displaystyle -6 - \frac {15} 2 = \frac {-27} 2 = b$

So, now, write your equation down:

$\displaystyle y = \frac 3 2 * x + \frac {-27} 2$

7. Thank you once again, although it's supposed to be 27/2 not -27/2

"passes through (4,2) and (0,8)"

9. Originally Posted by largebabies

"passes through (4,2) and (0,8)"
Find the slope:

$\displaystyle m=\frac{y_1-y_2}{x_2-x_1}=\frac{8-2}{0-4}=\frac{6}{-4}=-\frac{3}{2}$

From (0, 8) we know the y-intersept = 8.

Use the slope-intercept form of the general equation:

$\displaystyle y=mx+b$, where m is the slope, and b is the y-intercept.

$\displaystyle y=-\frac{3}{2}x+8$

10. that helped alot!

although i'm now stuck on another equation , I did the same thing with this and got y= -10/-2 when I needed -5/4.

The equation goes like this.

“passes through (-5,10) and (3,0)”

help?