Ab and bc form a right angle at point b. if a = (-3, -1) and b = (4, 4), what is the equation of bc? (a) x + 3y = 16 (b) 2x + y = 12 (c) -7x − 5y = -48 (d) 7x − 5y = 48

We look for the equation of the line AB
 We have then:
 y-yo = m (x-x0)
 m = (y2-y1) / (x2-x1)
 m = (4 - (- 1)) / (4 - (- 3))
 m = 5/7
 We choose an ordered pair:
 (xo, yo) = (4, 4)
 Substituting:
 y-4 = (5/7) (x-4)
 y = (5/7) x-20/7 + 4
 7y = 5x - 20 + 28
 7y = 5x + 8
 y = (5/7) x + 8/7
 The equation of the perpendicular line is:
 -7x - 5y = -48
 
 the equation of BC is:
 (C) -7x - 5y = -48