PreCalc
posted by Lynnette on .
Find the line of the equation that
hits y=4x^220 when x= 5 that is
perpendicular to 5x6=3y
My solution does not graphical show perpendicular lines, but algebraically it works lol Help!

when x=5
y = 4(5)^2  20 = 80
so you have the point (5,80)
the slope of 5x6 = 3y is 5/3
so the slope of the required line is 3/5
Now use whichever method you normally use to find the equation of a line given its slope and a point on it. 
Hi Reiny, Yes, I got that far. I even came up with a line, but am looking to see what others get as my line, when graphed, is not perpendicular to the other line mentioned in the prob (5x6=3y)

since the new line has slope 3/5, its equation must be
3x + 5y = k
point(5,80) on it ....
15 + 400 = k = 385
so new equation is 3x + 5y = 385 or
y = (3/5)x + 77
Since the slopes are negative reciprocals of each other, their graphs MUST be perpendicular.
Check your calculation of points and check the plotting of points 
I hope you're right since that's the equation I got too! I may be entering things into my calculator wrong. Using that is new to me. Thanks for all you're help!