To find the equation of the trend line in slope-intercept form (y = mx + b), we need to determine both the slope (m) and the y-intercept (b) from the points that the line passes through.
From the information given, the line passes through the points \( (0, 9) \) and \( (4, 8) \):
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Find the slope (m): The formula for the slope \( m \) is: \[ m = \frac{y_2 - y_1}{x_2 - x_1} \] Taking points \( (0, 9) \) and \( (4, 8) \): \[ m = \frac{8 - 9}{4 - 0} = \frac{-1}{4} \]
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Find the y-intercept (b): The y-intercept is the value of \( y \) when \( x = 0 \). From the point \( (0, 9) \), we immediately see that \( b = 9 \).
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Write the equation: Now, we can substitute the values of \( m \) and \( b \) into the slope-intercept form: \[ y = -\frac{1}{4}x + 9 \]
Thus, the correct response is:
y = -\frac{1}{4}x + 9