For this case we have the following equation:
![y + 1 = 2 (x - 3)](https://tex.z-dn.net/?f=y%20%2B%201%20%3D%202%20%28x%20-%203%29)
That can be rewritten in the form ![y = mx + b](https://tex.z-dn.net/?f=y%20%3D%20mx%20%2B%20b)
Where:
- m is the slope of the line
So, we have:
![y + 1 = 2 (x - 3)\\y + 1 = 2x-6\\y = 2x-6-1\\y = 2x-7](https://tex.z-dn.net/?f=y%20%2B%201%20%3D%202%20%28x%20-%203%29%5C%5Cy%20%2B%201%20%3D%202x-6%5C%5Cy%20%3D%202x-6-1%5C%5Cy%20%3D%202x-7)
Where:
is the slope
is the cut point
Carlota has the following points:
(-1, 3) and (2, 9)
To know if the line
passes through these points, we must replace them in the equation and the equality must be fulfilled. So:
Point (-1, 3):
Substituting:
![3 = 2 (-1) -7\\3 = -2-7](https://tex.z-dn.net/?f=3%20%3D%202%20%28-1%29%20-7%5C%5C3%20%3D%20-2-7)
It's false, equality is not met. The point (-1, 3) does not go through the line.
The equation written by Carlota is erroneous, the procedure to follow is:
Given
and
, we find the slope:
![m=\frac{(y2-y1)}{(x2-x1)}](https://tex.z-dn.net/?f=m%3D%5Cfrac%7B%28y2-y1%29%7D%7B%28x2-x1%29%7D)
![m=\frac{(9-3)}{(2-(-1))}](https://tex.z-dn.net/?f=m%3D%5Cfrac%7B%289-3%29%7D%7B%282-%28-1%29%29%7D)
![m=\frac{6}{3}](https://tex.z-dn.net/?f=m%3D%5Cfrac%7B6%7D%7B3%7D)
![m=2](https://tex.z-dn.net/?f=m%3D2)
We observe that the slope found by Carlota is the same. Let's see cut point "b". For this we substitute any of the points given in the equation:
![y = 2x + b](https://tex.z-dn.net/?f=y%20%3D%202x%20%2B%20b)
Substituting (2,9) we have:
![9 = 2 (2) + b\\9 = 4 + b\\b = 9-4\\b = 5](https://tex.z-dn.net/?f=9%20%3D%202%20%282%29%20%2B%20b%5C%5C9%20%3D%204%20%2B%20b%5C%5Cb%20%3D%209-4%5C%5Cb%20%3D%205)
Thus, Carlota's error was at the cut-off point. The correct equation of the line that passes through the given points is ![y = 2x + 5](https://tex.z-dn.net/?f=y%20%3D%202x%20%2B%205)
Answer:
The correct equation of the line that passes through the given points is ![y = 2x + 5](https://tex.z-dn.net/?f=y%20%3D%202x%20%2B%205)
Carlota's mistake was at the cutoff point