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. (1 point)
y – 1 = –(x + 7)
x – 7 = –9(y + 1)
y – 7 = (x + 1)
y – 7 = –9(

Question

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.  (1 point)
y – 1 = –(x + 7)
x – 7 = –9(y + 1)
y – 7 = (x + 1)
y – 7 = –9(

radar · Answer

What is the slope of the girder line?

radar · Answer

That is the first thing you need to know to solve this problem.

anonymous · Answer

like i  dont know any of this im lost

radar · Answer

y = -9x -9         The slope is the coefficient of the x term.  What is that?

anonymous · Answer

-9

radar · Answer

Excellent.  Now for a perpendicular line (the brace) the slope will be the negative of the reciprocal.  first what is the reciprocal of -9 ??

anonymous · Answer

-0.11111111111

radar · Answer

Here is an example of a reciprocal.
The reciprocal of -5 is 1/-5

anonymous · Answer

so its 1/-9

radar · Answer

Yes that is the decimal value but as a fraction it is -1/9.  Now what would the negative of -1/9 be?  It would be a 1/9       Do you follow so far?

anonymous · Answer

yes

anonymous · Answer

so would the answer be b

radar · Answer

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