Truble solving point slope equations.

[achingankle]

Hi I am working on point slope equations. I am not having trouble converting the information into the equation, I am just having trouble solving the equation. Here is one of the problems I worked on.
slope=-3/5
points(4,4)
equation y-4=-3/5(x-4)
First, i used multiplied to get rid of the parenthesis.
y-4=-3/5x-2and2/5s. I changed 2and 2/5s to an improper fraction.
y-4=-3/5x-8/5.
Then I moved the -4 over by adding it the the other side of the problem
y=-3/5x-8/5+4
I simplified
y=-3/5x+2 and 2/5
I changed the mixed number again and got
y=-3/5+12/5.
Is this the answer I should have gotten? If not, where am I going wrong?
Thank you

 

[galactus]

You could use the slope intercept form, y=mx+b.

The line has slope -3/5 and passes through (4,4).

\(\displaystyle 4=\frac{-3}{5}(4)+b\)

\(\displaystyle b=\frac{32}{5}\)

\(\displaystyle y=\frac{-3}{5}x+\frac{32}{5}\)

See where you went wrong?.

 

[achingankle]

No, I'm sorry, I'm still getting 12/5 0r -8/5. Am I multiplying wrong?

 

[chivox]

Hi I am working on point slope equations. I am not having trouble converting the information into the equation, I am just having trouble solving the equation. Here is one of the problems I worked on.
slope=-3/5
points(4,4)
equation y-4=-3/5(x-4)
----- This part is getting you into trouble. Don't make it more complicated than it is: you know the slope and one point on the line. With that information, you can just use the form "y = mx + b" and plug in the point given, (x, y) = (4, 4). Then, solve for b using algebra, since that will be the only unknown left. At that point, the equation of the line is y = mx + b, where m is the slope and b is the value you found from your work.

That is, using the slope-intercept form of the equation for a line,

y = mx + b

Subtitute the point that you know is on the line:

4 = (-3/5) (4) + b

And solve for b:

4 - (-3/5) (4) = b

\(\displaystyle \frac{20}{5} - \frac{-12}{5} = b\)

\(\displaystyle \frac{32}{5} = b\)

(because we subtract a negative value, which means we add.)

Then, the equation is just: y = (-3/5) x + b

where b is the value you found....

 

[wjm11]

slope=-3/5
points(4,4)
equation y-4=-3/5(x-4)
First, i used multiplied to get rid of the parenthesis.
y-4=-3/5x-2and2/5s. I changed 2and 2/5s to an improper fraction.
y-4=-3/5x-8/5.

Achingankle,

Your approach and steps are fine. Just watch your multiplication. That’s where your mistake is.

-3/5(x-4) = (-3/5)(x) + 12/5

I recommend you not even use “2and 2/5” in your work; stick to the improper fractions all the way through.

Continuing,

y-4= (-3/5)(x) + 12/5 Next add 4 to both sides of the equation:

y = (-3/5)(x) + 12/5 + 20/5

(Note: we changed 4 to 20/5 to have a common denominator with 12/5.) Next, simplify:

y = (-3/5)(x) + 32/5

 

[Denis]

y-4=-3/5(x-4)

Or rewrite the thing so it's clear:
y - 4 = [-3(x - 4)] / 5

Now you can "see" that all you need to do is multiply by 5:
5(y - 4) = -3(x - 4) : kapish?

 

[achingankle]

Thank you, This is helping me tons!