-9x(x+3)=18

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Solution for -9x(x+3)=18 equation:



-9x(x+3)=18
We move all terms to the left:
-9x(x+3)-(18)=0
We multiply parentheses
-9x^2-27x-18=0
a = -9; b = -27; c = -18;
Δ = b2-4ac
Δ = -272-4·(-9)·(-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{-(-27)-9}{2*-9}=\frac{18}{-18} =-1 $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-27)+9}{2*-9}=\frac{36}{-18} =-2 $

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