Line segment AB has a slope of 5/4 and contains point A(8,-7). what is the y-coordinate of point Q(3,y), if QA is perpendicular to line segment AB?
A. y = -2
B. y = -3
C. y = 1
D. y = 3
+5265 SO, perpendicular lines mean the slope is the opposite reciprocal of the given one.
5/4, opposite reciprocal is -4/5.
Let's see here...
We can test these values on a graph by graphing the equation.
So, from the point and the slope given, I've found the y-intercept to be -3.
I believe the y-intercept is opposite, but not a reciprocal.
Hmmm..... I've been graphing for a bit but I don't think that strategy is going to work. Cphill, can you take it from here?
+5265 SO, perpendicular lines mean the slope is the opposite reciprocal of the given one.
5/4, opposite reciprocal is -4/5.
Let's see here...
We can test these values on a graph by graphing the equation.
So, from the point and the slope given, I've found the y-intercept to be -3.
I believe the y-intercept is opposite, but not a reciprocal.
Hmmm..... I've been graphing for a bit but I don't think that strategy is going to work. Cphill, can you take it from here?
+130477 You were on the right track, rarinstraw [I gave you 5 pts].....
Note that rarinstraw was correct......the slope of QA = -4/5
So...the slope between A and Q = -4/5...and we need to solve this :
[-7 - y] / [8 - 3] = - 4/5 cross-multply
5[-7-y] = -4 [ 8 - 3] simplify
-35 - 5y = -4 [5]
-35 - 5y = -20 add 35 to both sides
-5y = 15 divide both sides by -5
y = -3 ...just as rarinstraw found ....!!!!
