Answer:
.19
Step-by-step explanation:
X ≥9 years after 2009.
Y=4x+4
Y-4=4x
X=(Y-4)/4
Y=number of U.S. households, in millions.
Y≥40
Y-4≥36
(Y-4)/4≥9
So, X≥9.
x= (-3 +- sqrt3)/2
