18.5k views
2 votes
What is the equation of the line that is perpendicular to y = one-fifth x + 4 and that passes through (5,–4)?

1 Answer

1 vote

Answer:

y= -5x + 21

Explanation:

The equation of the line that passes through (5, -4) and is perpendicular to line y = 1/5x + 4 is y= -5x + 21

The slope that is perpendicular to the slope 1/5x is -5x.

To find a perpendicular slope, you take the negative reciprocal. (so you change the signs (1/5x is positive so now it would be negative) and -5/1 is basically -5)

However, y = -5x + 4 does NOT pass through (5, -4)

But we still have to write the equation in slope intercept form or the equation of the line

The formula for slope- intercept form is : y= mx + b

So we must plug in (m) which is our -5x and for y we look at the coordinates they gave us ----- (5, -4). -4 is our y. In the coordinates we also have x listed which is 5, so we all plug that in.

y = -5x + b (as you can see -5x is plugged in here)

-4 = -5x + b (as you can see -4 is plugged in here)

4 = -5(5) + b (as you can see 5 is plugged in here)

NOW WE MUST SOLVE!

Isolate B

-4 = -25 + b

Add 25 from both sides.

-4 = -25 + b

+25 25

----------------

21 = b

We can now plug this into our slope intercept formula---y= mx+ b---to find the equation of the line.

Therefore, y = -5 x +21

User James Johnson
by
6.5k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.