finding the equation having the given slope and the points

[Roselynn29]

m=6/7,(2,-4)

y(-4)=(6/7)+(x+2)

y+4=6/7x-

This is as far as I get. I do not understand how they come up with the second fraction set. Please help.

 

[Denis]

Did you miss math classes?

http://www.ugrad.math.ubc.ca/coursedoc/ ... qline.html

 

[tutor_joel]

y = mx + b

you know the point (2, -4)

x = 2
y = -4

Set up and Solve the equation for b

 

[soroban]

Hello, Roselynn29!

You're close, but your notation is sloppy. . .

\(\displaystyle m=\tfrac{6}{7},\;(2,-4)\)

. . \(\displaystyle \boxed{\begin{array}{c}\text{Point-slope Formula} \\ \\ \text{Given a point }(x_1,y_1)\text{ and slope }m, \\ \text{ the equation of the line is:} \\ y - y_1 \;=\;m(x-x_1) \end{array}}\)


\(\displaystyle \text{So we have: }\;y - (\text{-}4) \;=\;\tfrac{6}{7}(x - 2)\)

. . . . . . . . . . .\(\displaystyle y +4\:=\:\tfrac{6}{7}x - \tfrac{12}{7}\)

. . . . . . . . . . . . . \(\displaystyle y \;=\;\tfrac{6}{7}x -\tfrac{40}{7}\)

 

[Roselynn29]

Okay so I see the 12/7 but how did you come up with the 40/7???

 

[mmm4444bot]

Okay so I see the 12/7 but how did you come up with the 40/7? You mean -40/7, yes?

Look at the equation:

y + 4 = (6/7)x - 12/7

To solve for y, we subtract 4 from both sides.

On the righthand side, -12/7 minus 4 equals -40/7.

If you would like to review arithmetic with fractions, go HERE.

 

[Roselynn29]

Why would the answer be -40/7 instead of -8/7? This is where Algebra makes no sense to me...I am taking Accounting and really do not need this information except for the fact that it is a required course to pass.

 

[mmm4444bot]

Why would the answer be -40/7 instead of -8/7? Because we don't do arithmetic that way with fractions.

This is where Algebra makes no sense to me It's not algebra. It's 4th-grade arithmetic (at least it was when I went to grade school).

If you need to refresh your memory on how to subtract 4 from -12/7, go to the lessons on subtracting fractions (11 & 12) at the site I previously referenced for you.

It will show you how to get a common denominator for the fractions in the subtraction -12/7 - 4/1.

 

[mmm4444bot]

I am taking Accounting and really do not need this information

Accountants need logic skills.

Studying algebra is an excellent way to develop logic skills.

As an accountant, what will you do during a power failure or some situation where you have nothing but paper and pencil, if you need to add or subtract fractions?

 

[Denis]

Why would the answer be -40/7 instead of -8/7?

-12/7 - 4 = -12/7 - 28/7 = -40/7 ; same way as -2 - 3 = -5