Solve the problem.A tank initially contains 120 gal of brine in which 60 lb of salt are dissolved. A brine containing 3 lb/gal of salt runs into the tank at the rate of 9 gal/min. The mixture is kept uniform by stirring and flows out of the tank at the rate of 7 gal/min. Write, in standard form, the differential equation that models the mixing process.
A. 
+ 
y = 27
B. 
= 27 - 
y
C. 
+ 
y = 21
D. 
+ 
y = 27
Answer: A
Mathematics
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Find the focus and the directrix of the parabola.-2y2 - 12y - 14 - x = 0
A. Focus: 
; directrix: x = 
B. Focus: (-7, 4); directrix: x = -9
C. Focus: 
; directrix: y = 
D. Focus: 
; directrix: x = 
Mathematics
Solve the problem.Use the comparison line graph to determine who needed more time to prepare for Test 1, Jennifer or David.
A. Jennifer B. David
Mathematics
Write the partial fraction decomposition of the rational expression.
A. 
+ 
+ 
B. 
+ 
+ 
C. 
+ 
+ 
D. 
+ 
+ 
Mathematics
Determine whether the following represents a function.
A. function B. not a function
Mathematics