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Select the correct answer.

What is the equation of the line that goes through the points [tex]$(-5,-1)$[/tex] and [tex]$(5,5)$[/tex]?

A. [tex]$y = \frac{3}{5}x - 8$[/tex]
B. [tex][tex]$y = \frac{2}{5}x + 3$[/tex][/tex]
C. [tex]$y = \frac{3}{5}x + 2$[/tex]
D. [tex]$y = \frac{2}{5}x - 7$[/tex]


Sagot :

To determine the equation of the line that passes through the points [tex]\((-5, -1)\)[/tex] and [tex]\( (5, 5) \)[/tex], we can follow these steps:

1. Calculate the slope (m):

The formula for the slope of a line between two points [tex]\((x_1, y_1)\)[/tex] and [tex]\((x_2, y_2)\)[/tex] is:
[tex]\[ m = \frac{y_2 - y_1}{x_2 - x_1} \][/tex]

Plugging in the coordinates of our points:
[tex]\[ m = \frac{5 - (-1)}{5 - (-5)} = \frac{5 + 1}{5 + 5} = \frac{6}{10} = \frac{3}{5} \][/tex]

2. Find the y-intercept (b):

The slope-intercept form of a line is defined as:
[tex]\[ y = mx + b \][/tex]

To find [tex]\( b \)[/tex], we use one of the points and the calculated slope. We will use the point [tex]\((-5, -1)\)[/tex]:
[tex]\[ y = mx + b \implies -1 = \frac{3}{5} \cdot (-5) + b \][/tex]

Then, solve for [tex]\( b \)[/tex]:
[tex]\[ -1 = \frac{3}{5} \cdot (-5) + b \implies -1 = -3 + b \][/tex]
[tex]\[ -1 + 3 = b \implies b = 2 \][/tex]

3. Write the equation of the line:

Using the slope [tex]\( \frac{3}{5} \)[/tex] and the y-intercept [tex]\( 2 \)[/tex], the equation of the line is:
[tex]\[ y = \frac{3}{5} x + 2 \][/tex]

Now we compare this equation with the given options and find that:
[tex]\[ \boxed{y = \frac{3}{5} x + 2} \][/tex]

Therefore, the correct answer is:
[tex]\[ \boxed{C} \][/tex]