Posted by Rudy on .
Write an equation of the line that passes through the point (i) parallel to the given value, and (ii) perpendicular to the given line.
Point(7,1) Line(5x5y=90)

Calculus 
Reiny,
The given line is 5x  5y = 90
or , dividing by 5
x+y = 18
since the new line is parallel to it, its equation differs only in the costant, so let the new equation be
x+y = c , but (7,1) lies on it, so
7+1=c = 8
equation: x+y=8
If perpendicular, then the slop must be negative reciprocal : 1 > 1/1 = 1
new equation:
xy = k
but (7,1) on it, so
71 = k = 6
x  y = 6