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2x^2-9x-39=0
a = 2; b = -9; c = -39;
Δ = b2-4ac
Δ = -92-4·2·(-39)
Δ = 393
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-\sqrt{393}}{2*2}=\frac{9-\sqrt{393}}{4} $$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+\sqrt{393}}{2*2}=\frac{9+\sqrt{393}}{4} $
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