Question

Slope: When the slope is -2/3, the author says "if we go over by 1, we gonna go down by 2/3rds". How is this possible? What's the mathematical process through which he determines this?

Answer 1

slope is defined to be the change in y values divided by the change in x values

Answer 2

I know what is slope, and I know that in -2/3rds when you go over by 2, you go down by 3. But how do you then translate this for smaller values? How do you get from -2/3 to -1 over 2/3?

Answer 3

-2/3
----- = (-2/3)/1
3

Answer 4

instead of moving by -2 and 3; move by 1/3 less

Answer 5

or, we can simply define it as the equation:

y = -2/3 x

when x=1, y=-2/3

Answer 6

isn't -2/3 divided by 3 -2/9?

in reply to
-2/3
----- = (-2/3)/1
3

Answer 7

depends on how you read my notation :/

Answer 8

divide both top and bottom by 3

Answer 9

or, we can simply define it as the equation:

y = -2/3 x

when x=1, y=-2/3

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this made a lot of sense

Answer 10

i knew something has to :)

Answer 11

Unfortunately it doesn't seen to make sense yet,

in another example when the slope m=3, he says that if x is equal to 0, y is equal to 1.

so if we use the previous formula y = 3 * 0 , it means y is zero as well, which doesn't hold true.

Answer 12

that just means that at x=0, y=1 which is the point at which the line intercepts or cross the y axis

Answer 13

y = slope*x + yintercept

Answer 14

there are an infinity of lines that can have the same slope; they are defined specifically by where they cross, intercept, the y axis

Answer 15

so in this case:

y = 3x + c would ba a family of lines; and we want the one that when x=0, y=1

y = 3x + 1 satisfies that requirement

Answer 16

it is commonly seen as:

y = mx + b

Answer 17

I'm sorry but I didn't get you, can someone else please reply, will try to open a new question.

Answer 18

the y = 3x still applies; but we are given new information such that when x=0, y=1

y = 3*0 = 0 so we have to adjust this to match the given information;

when does 0 equal 1?

Answer 19

http://www.khanacademy.org/math/algebra/linear-equations-and-inequalitie/v/graphs-using-slope-intercept-form I'm talking about this specific video, he's talking about finding the m if you have the slope only

Answer 20

*the b

Answer 21

you cant find b if you only have a slope; you need to know more about the situation; you need to know at least one other point that the line cross thru, or anchors to

Answer 22

the b is defined as the point where the line crosses the y axis; its refered to as the y-intercept

Answer 23

yeah we also know the x,y but he's trying to find the b non-algebrically by guessing somehow