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Posted on 2016-08-31
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I dont understand the formula -b/2a. I know quadratic equation ax2+bx+c but i dont know where this formula comes from?
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Question by:mustish1
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Expert Comment

ID: 41779081
From calculus   x = -b/2a  is the value where the parabola will have its max or min value.  In this case (with a= -11) it will be a maxim.
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LVL 27

Expert Comment

ID: 41779089
Your graph is a sinusoid not a parabola.
If you use the quadratic formula you will find the (usually) two places where the function equals zero.
x = -b/2a is halfway between the zeroes, and will be the location of the max (or min).
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Author Comment

ID: 41779135
what is this formula: f(50/11)
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Accepted Solution

d-glitch earned 2000 total points
ID: 41779170
a = -11     b = 100     -b/2a = (-100)/(2*(-11) = 50/11

f(50/11)  means evaluate the quadratic function at x = 50/11 to find the maximum.

For example      f(x=0) is 8     f(x=1) is 87    f(x=-1) is -103  and the graph should be symmetric around x=50/11.
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Author Closing Comment

ID: 41780095
Thank You.
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