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Write the equation of a line perpendicular to 5x−9y=−8 that passes through the point ​(−5​,8​).

User Richard Hoskins
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1 Answer

21 votes
21 votes

Answer: y = -(9/5)x - 1

Explanation:

Rewrite the equation in standard form: y = (5/9)x+(8/9). [y=mx+b]

A line perpendicular to this would have a slope that is the negative inverse of the original slope (5/9), which would make it -(9/5). The y-intercept would also change, but we don't know the value, yet. For now, we'll use "b" for the y-intercept. This results in a perpendicular line:

y = -(9/5)x + b

We can calculate b, the y-intercept, by using the point (-5,8) and solving for b.

8 = -(9/5)*(-5) + b

8 = (9) + b

b = -1

The line perpendicular to 5x−9y=−8 that passes through the point ​(−5​,8​) is

y = -(9/5)x - 1

User Thiago Pereira
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2.5k points