Question

Solve |9 – 4x| > 7 and write interval notation for the solution set.

A.(1/2, 4)
B. (-4,-1/2)
C. (1/2, infinity)
D. (-infinity U (4, infinity)

I say the answer is D..Am i correct?

Answer 1

Undo the absolute value by considering the two possible solutions:

9 - 4x > 7

and 9 - 4x < -7

Solve each separately:

9 - 4x > 7
-4x > -2
x < 1/2

9 - 4x < -7
-4x < -16
x > 4

The answer should be (-infinity, 1/2) U (4, infinity).

You appear to have left off the 1/2 in copying answer D. However, it appears to be answer D.

Answer 2

Yes i left off the 1/2 by mistake, but D is the answer like i said? Thanks!