Question

HELP ME PLEASE! i will give MEDALS!! its multiple choice! I'm not sure how to solve this. Plans for a bridge are drawn on a coordinate grid. One girder of the bridge lies on the line y= -9x -9. A perpendicular brace passes through the point (-1, 7). Write an equation of the line that contains the brace.
The multiple choice is
a. y-1= -1/9 (x+7)
b. x-7= -9 (y+1)
c. y-7= 1/9 (x+1)
d. y-7= -9 (x+1)
(The 1/9 is a fraction not division!)

Answer 1

I believe it is C. Do you want an explanation?

Answer 2

Yes please thank you so much!

Answer 3

For any perpendicular lines, the slopes are always opposite reciprocals. So in this case, the slope of the equation given is -9. You tell me what is the opposite reciprocal of -9?

Answer 4

First find the slope of y= -9x -9. let us compare it with y=mx+c we find that:
slope m1=-9
therefopre slope of the brace passes through the point (-1, 7) would be
\[m_2 = \frac{1}{9}\]
Now equation of line in slope point form is given as :

y-y1=m2(x-x1)
y-7=1/9(x-(-1))
y-7=1/9(x+1) is the required equation of the brace.

Hence option c. y-7= 1/9 (x+1) is the correct answer.

@nialler143

Answer 5

Thank you both so much! This is very helpful :) I have one more question would one or both of you mind trying to help?

Answer 6

Sure. I will see if I can help.

Answer 7

okay thank you here is it.
Write a paragraph proof of this theorem: In a plane, if two lines are perpendicular to the same line, then they are parallel to each other.
Given that r is perpendicular to s, t is perpendicular to s..
Prove that r is parallel to t

Answer 8

If r is perpendicular to s, then by the definition of perpendicular lines angle 4 has a measure of 90 degrees. Using the same logic with line t, angle 6 is 90 degrees. Since the same side interior angles are supplementary, line r is parallel to line t.

I found this image online, and it looked like it went along with this. http://tinypic.com/view.php?pic=rszvdg&s=5#.UlQ43BAixus Hope this helped.

Answer 9

Yes! thank you again!