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Versions of Linear Equations Quick Check
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Question
A line passes through the points (7.5,−2)
and (−5,8)
. What is the equation of the line in slope-intercept form?(1 point)
Responses

y=−4/5x+4
y equals negative Start Fraction 4 over 5 End Fraction x plus 4

y=4/5x+4
y equals Start Fraction 4 over 5 End Fraction x plus 4

y=5/4x+4
y equals Start Fraction 5 over 4 End Fraction x plus 4

y=5/4x−2

1 answer

To find the equation of the line that passes through the points \((7.5, -2)\) and \((-5, 8)\) in slope-intercept form (which is \(y = mx + b\), where \(m\) is the slope and \(b\) is the y-intercept), we first need to calculate the slope (\(m\)).

The formula for the slope between two points \((x_1, y_1)\) and \((x_2, y_2)\) is:

\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]

Here, \((x_1, y_1) = (7.5, -2)\) and \((x_2, y_2) = (-5, 8)\).

Calculating the slope:

\[ m = \frac{8 - (-2)}{-5 - 7.5} = \frac{8 + 2}{-5 - 7.5} = \frac{10}{-12.5} = -\frac{4}{5} \]

Now we have the slope \(m = -\frac{4}{5}\).

Next, we can use either point to find the y-intercept \(b\) using the slope-intercept form \(y = mx + b\). Using the point \((7.5, -2)\):

\[ -2 = -\frac{4}{5}(7.5) + b \]

Calculating \(-\frac{4}{5}(7.5)\):

\[ -\frac{4}{5} \cdot 7.5 = -6 \]

So we have:

\[ -2 = -6 + b \]

Solving for \(b\):

\[ b = -2 + 6 = 4 \]

Now we can write the equation of the line:

\[ y = -\frac{4}{5}x + 4 \]

From the given options, the correct response that matches this equation (in slope-intercept form) is:

\[ y = -\frac{4}{5}x + 4 \]