Question

The graphs of two linear equations ax + by = c and bx - ay = c, where a, b, c are all not equal to zero.

A. Are parallel
B. Intersect at on point but are not perpendicular
C. Intersect at two points
D. Perpendicular

Answer 1

Let us find the slopes of the two lines

ax+by=c, slope m1 = -a/b

bx-ay=c, slope m2 = b/a

m1*m2 = (-a/b)(b/a) = -1

Therefore the two lines are perpendicular so the answer is D