Answer:
x = -5.6
Step-by-step explanation:
Using the given coordinates in the given slope formula, we have ...
(y2 -y1)/(x2 -x1) = -8/5 . . . . . using the given slope
Setup
(4 -x)/(3 -9) = -8/5 . . . . substituting (9, x) for (x1, y1) and (3, 4) for (x2, y2)
Solution
Multiplying by 30, we have ...
5(x-4) = -48
5x -20 = -48 . . . . eliminate parentheses
5x = -28 . . . . . . . . add 20
x = -5.6 . . . . . . . . divide by 5
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Additional comment
In the attachment, we have written the point-slope equation of the line, then found the point on that line that has a x-coordinate of 9. We see the y-coordinate of that point is -5.6, as computed above.
If you swap the points (x1, y1) and (x2, y2), then the slope equation ends up with fewer minus signs to handle.
