The points (-1, r) and (2, 1) lie on a line with slope 2. Find the missing coordinate r
2 answers:
9514 1404 393
Answer:
r = -5
Step-by-step explanation:
The x-coordinate of the partially-defined point is 3 units less than the x-coordinate of the given point. The slope of 2 tells you the y-coordinate of the partial point (r) will be 2·3 = 6 units less than the y-coordinate of the given point. That is ...
r = 1 - 2·3
r = -5
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You are given the slope of the line and a point on it, so you can write the point-slope equation of the line:
y -y1 = m(x -x1) . . . . . . . line with slope m through point (x1, y1).
For the given point and slope, this is ...
y -1 = 2(x -2)
For an x-value of -1, the corresponding y-value will be ...
r = 2(-1-2) +1 = -6 +1
r = -5
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