Answer:
X ≥9 years after 2009.
Step-by-step explanation:
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.
Vertex is at the point ( h , v )
The equation of a parabola is:
x = a ( y - v )² + h
Answer: B )
First case:
average of test score =70
number of students =p
total score of 'p' students = ( average of test score)*( number of students)
total score of 'p' students =70p
Second case:
average of test score =92
number of students =n
total score of 'n' students = ( average of test score)*( number of students)
total score of 'n' students =92n
total number of students = p+n
total average score =86
so, total score =86(p+n)
total score = total score of 'p' students +total score of 'n' students

now, we can simplify it



now, we can find p/n

................Answer