SOLUTION: Arrange the problem is represented by the equations in increasing order with respect to the Y values of the directrixes. y=-x^2+3x+8 y=2x^2+15x+18 y=x^2+13x+5 y=-2x^2+4x+8

Question 1085007: Arrange the problem is represented by the equations in increasing order with respect to the Y values of the directrixes.
y=-x^2+3x+8
y=2x^2+15x+18
y=x^2+13x+5
y=-2x^2+4x+8
Answer by AnlytcPhil(1806) (Show Source): You can put this solution on YOUR website!









Complete the square on the left:

       
       





Compare to



, , , 

The equation of the directrix is 



 <-- equation of directrix

----------------------

y=-x^2+3x+8, substitute in above, a=1, b=3, c=8, directrix: y = 6 

y=2x^2+15x+18, substitute a=2, b=15, c=18, directrix: y = -10 

y=x^2+13x+5, substitute a=2, b=13, c=5, directrix: y = -37 

y=-2x^2+4x+8, substitute a=-2, b=4, c=8, directrix: y = 9.975

Edwin

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