Line c has a slope of 5/9. Line d is perpendicular to c. What is the slope of line d?
The slope of a line perpendicular to a line with slope m is equal to the negative reciprocal of m. So, if line c has a slope of 5/9, then the slope of line d would be -9/5.
Explain, because I don't understand.
When two lines are perpendicular, their slopes are negative reciprocals of each other. In other words, if the slope of one line is m, the slope of the line perpendicular to it would be -1/m.
In this case, the slope of line c is 5/9. So, the slope of the line perpendicular to c (line d) would be -1/(5/9) = -9/5.
By taking the reciprocal of 5/9 and then flipping the sign, you get the slope of line d.