Question

If the graphs of linear functions f(x)=2x+9 and g(x)=−ax+9 are perpendicular, what is the value of a?

a) -2
b)-1/2
c)-9/2
d)1/2
e)2

Answer 1

d) 1/2

Explanation:

The slopes of perpendicular lines multiply to give -1. Here, the slopes of the lines are 2 (for f(x)) and -a (for g(x)).

... 2·(-a) = -1

... a = -1/-2 = 1/2 . . . . . . divide by the coefficient of a