equation through the points (8, 1) and (-2, -17)

jehan.the.great

New member
Joined
Apr 25, 2006
Messages
8
write the equation of the lines that passes through the given two points:
a.(8, 1) (-2, -17)


?????????????
i'm soooooo lost
 
Well the change in y is –18.
The change in x is –10.
Slope is change in y divided by change in x.
 
Go to your text material.
Look up slope.
Then look up point slope form.
That will tell you how to do this problem.

The point being that we will not do it for you.
(Well maybe Soroban or guntram will?)
 
guntram

guntram said:
I have a mistake
the right answer y=1.8x-13.4

I tried solving the problem and came out with 1.8 but lost where -13.4 came from?

I used y1 -y2 / x1 - x2
1 - (-17) = 18

8 - (-2) = 10


18/10 = 1.8

How did you get -13.4 and where?
 
Hello, jehan.the.not.so.great!

Write the equation of the lines that passes through: (8, 1) (-2, -17)
You're expected to know something about lines . . . like some formulas?

Slope of line through \(\displaystyle (x_1,y_1)\) and \(\displaystyle (x_2,y_2):\;\;m\;=\;\frac{y_2\,-\,y_1}{x_2\,-\,x_1}\)

Equation of line through \(\displaystyle (x_1.y_1)\) with slope \(\displaystyle m:\;\;y\,-\,y_1\;=\;m)x\,-\,x_1)\)


We're given two points: \(\displaystyle \,P(8,1),\;Q(-2,-17)\)

The slope of line \(\displaystyle PQ\) is: \(\displaystyle \,m\;=\;\frac{-17\,-\,1}{-2\,-\,8}\;=\;\frac{-18}{-10}\;=\;\frac{9}{5}\)
'
The line through \(\displaystyle (8,1)\) with slope \(\displaystyle m\,=\,\frac{9}{5}\) is: \(\displaystyle \;y\,-\,1\;=\;\frac{9}{5}(x\,-\,8)\)

Simplify and we get: \(\displaystyle \: y \;= \;\frac{9}{5}x\,-\,\frac{67}{5}\)


. . . and don't use decimals in algebra!
 
Top