Why was this question marked wrong? (Concavity)

[stadtaffe2]

For which values of X is Y = 2x^3 - 6x^2 Concave Down?

Y' =6x^2 - 12x =0
Y''=12X -12 = 0
X=1

X>1
Test Point 2
24-12 = 12
Concave up

x<1
Test Point 0
12(0) -12 = -12
Concave Down


I wrote (X<1)

What about this answer is incorrect?

 

[galactus]

They probably wanted it written as concave down on \(\displaystyle (-\infty, \;\ 1)\)

The inflection point is at x=1, so it is concave up on \(\displaystyle (1, \;\ \infty)\)