What is the equation of the line that is perpendicular to y = 7/9x + 15 and goes through the point (-1, 2)?
A. 9x + 7y = 5
B. 9x + 7y = -5
C. 9x + 7y = 23
D. 9x + 7y = -23
My work:
y - 2 = 7/9 (x + 1)
y - 2 = 7/9x + 7/9
2 + 7/9 = 2 7/9
y = 7/9x + 2 7/9
I'm assuming that, because the line is perpendicular, the answer must be negative, so I'd figure it'd either be B or D.
the slope of the new line must be -9/7
so equation is:
y-2 = (-9/7)(x+1)
7y -14 = -9x - 9
9x + 7y = 5 ------ A
You even said that you knew the slope had to be negative (true), so why did you use a positive slope ???