<PRE><B>Question 273005</B>
How do I find a root of the equation 2x^2-x-15=0
Think of two numbers whose product is -15*2 = -30
and whose sum is -1
The numbers are -6 and +5
Replace -x by -6x+5x and factor:
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2x^2 -6x + 5x - 15 = 0
2x(x-3) + 5(x-3) = 0
(x-3)(2x+5) = 0
x = 3 or x = -5/2
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ALSO 
How do I find the x coordinate of the vertex for the quadratic equation x^2+6x+5=0
The x-value of the vertex is -b/2a = -6/(2*1) = -3
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Cheers,
Stan H. 
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