Question 3 (Essay Worth 10 points) (01.04 MC)The elevation of city A is 60 feet above sea level; the elevation of city C is 12 feet above sea level. The elevation of city Dis of the elevation of city c.
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Part A: Write an expression to represent the elevation, in feet, of city D. (5 points)
Part B: Solve the expression and explain why the answer is negative or positive. (5 points)

solution:

the given function is ,

      =

the three roots of this quadratic function is , 0 ,8 and 10.all the roots are real and rational.

if a quadratic equation is of the form ,

sum of the roots = a + b +c= 0+8+10=18=  

product of roots taken two at a time = a b + b c+ c a = 0+80+0=80 =  

product of roots = a b c = 0=  

there are 11 doors in a hall starting from 0 to 11.the entry in the hall is permitted through gate number 0 and exit is allowed through only gate number 8 and 10.so, three roots(0,8,10) of quadratic function is given by entry and exit route of this hall.