With a root of -1/2 it is likely that 2x^2 + 15x + p = 0 can be written as:
(2x + 1)*(x - a) = 0 This has roots of -1/2 and a
Expanding this we get: 2x^2 +(1 - 2a)*x - a = 0
For this to match we must have: 1 - 2a = 15 or a = -7
We must also have p = -a so p = 7
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