-18=2x2+15x

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Solution for -18=2x2+15x equation:



-18=2x^2+15x
We move all terms to the left:
-18-(2x^2+15x)=0
We get rid of parentheses
-2x^2-15x-18=0
a = -2; b = -15; c = -18;
Δ = b2-4ac
Δ = -152-4·(-2)·(-18)
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-9}{2*-2}=\frac{6}{-4} =-1+1/2 $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+9}{2*-2}=\frac{24}{-4} =-6 $

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