SOLUTION: Please help me solve this question. Find the equation of the line joining A(-1, -9)to B(6, 12) Another line passes through C(7, -5) and meets AB at right angle at D. Find the

Question 70222: Please help me solve this question.
Find the equation of the line joining A(-1, -9)to B(6, 12)
Another line passes through C(7, -5) and meets AB at right angle at D. Find the equation of CD and calculate the coordinates of D.
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
To find the slope from A(-1, -9)to B(6, 12) use

Now use the general slope-intercept equation of a line y=mx+b and solve for b.
Plug in point B(6,12) either point will work

So the equation is

To find the equation from C to D, we need to invert and negate the slope of our previous answer. This makes the new slope perpendicular to the old slope.

Now plug in the point C to solve for b

So the equation of the line that passes through CD is

To verify this answer, you can graph these lines and plot the points. A good program for this on the PC is Winplot (http://math.exeter.edu/rparris/winplot.html ) which allows quick and efficient graphing, and allows you to plot points.
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