Graphing a line given its equation in slope-intercept form

bobmane

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I am being asked to solve for and then plot a line.
There are two versions of the problem.
One that requires doing multiplication like:
y = -2x + 5
That i know how to do.
and another that has negative fraction like
y = -1/2 +1
That one is confusing. Even when they give me the answer I am not seeing how they did the math.
Or other similar examples like y = -2/3 x 3 + 5 or y = -2/3 x 6 + 5
I attached an image of the answer they are giving:
1572719412951.png
 
and another that has negative fraction like
y = -1/2[x] +1
That one is confusing. Even when they give me the answer I am not seeing how they did the math.
Or other similar examples like y = -2/3 x 3 + 5 or y = -2/3 x 6 + 5
Are you saying that when you multiply [MATH]-\frac{1}{2}\cdot2-4[/MATH], you don't get -5, or something else?

If so, here's the work, in more detail:

[MATH]-\frac{1}{2}\cdot 2-4 = \frac{-1}{2}\cdot\frac{2}{1}-4 =-1-4 = -5[/MATH]​

Does that clear it up? If not, please show your work on a problem like this, so we can see what goes wrong.
 
You should pick multiples of 2's for x as you are multiplying x by 1/2. That 2 in the denominator WILL go into x evenly if x is a multiply of 2. Same if you have to multiply 1/3 by x. Let x be a multiple of 3.
As far as the signs go, just find the sign of the number that x is being multiplied by and the sign of x. If they are the same the results is positive, else it is negative.
 
Does that clear it up? If not, please show your work on a problem like this, so we can see what goes wrong.

In the other example, of Y = - 1/2 x 4 - 4
I would do:
-1/2 X 4/1 = -1 x 4 = -4 (not sure what to do with denominator) then -4 - 4 = -8 - but the answer as shown above is -6
 
Do you not know how to multiply fractions?

-1/2 times 4 is -2, not -4. Then -2 - 4 = -6.

When you multiply fractions, you multiply the numerators (in your example, -1*4 = -4), and you multiply the denominators (2*1 = 2). The product is -4/2, which simplifies to -2. You can also simplify before multiplying, but we should stick to one thing at a time.

For advice on fractions, you might go here: https://www.mathsisfun.com/fractions_multiplication.html
 
In the other example, of Y = - 1/2 x 4 - 4. If the x means times, then how can anyone know if when you write an x if you mean the variable x or a symbol for multiplication?
Y = (-1/2)x - 4. So x = 4
Clearly you just can't ignore the 2 in the denominator.
So you need to compute (-1/2)(4) - 4
Let's look at (-1/2)(4) first. There are to steps. One is to get the sign and another is to get the number. The sign of (-1/2) is negative and the sign of 4 is positive. So the final sign is negative (since -*- = +). Now onto finding the number, since we found the sign we can ignore the signs, (1/2)*4 can (and SHOULD) be read as half of four. Well 1/2 of 4 is 2. So we now know that (-1/2)*4 = -2
Let's finish up: (-1/2)(4) - 4 = -2 -4. You take away 2 and then take away 4 you took away 6. So (-1/2)(4) - 4 = -6.
 
In order to do the multiplication you must do reciprocal so in - 1/2 * 4 then you would do - 1/2 * 1/4 not * 4/1 ??
 
In order to do the multiplication you must do reciprocal so in - 1/2 * 4 then you would do - 1/2 * 1/4 not * 4/1 ??
No...No.... Double No...

You MAY use reciprocal to conduct DIVISION.

Please try to justify your work as you go along - do NOT blindly follow "must do" methods.
 
In order to do the multiplication you must do reciprocal so in - 1/2 * 4 then you would do - 1/2 * 1/4 not * 4/1 ??
You need to think that comment though as I am 100% sure that you know that it is not true.

I am sure that you know what 6*2 equals and I am equally sure that you do not get that by computing 6*(1/2)

Here is a reason that can't work. If in multiplication you keep the 1st number and then multiply by the reciprocal of the 2nd number here is what happens.

6*2 becomes 6*(1/2). But then 6*(1/2) becomes 6*2. Then 6*2 becomes 6*(1/2) etc.... So which is correct?

Also if you multiply 6 by different numbers you should expect to get different answers. Since 2 and 1/2 are different numbers (after all you rather your boss pays you for 6 hours than for 1/2 an hour). So 6*2 can not be 6*(1/2)
 
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