x2-15x=18

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Solution for x2-15x=18 equation:



x2-15x=18
We move all terms to the left:
x2-15x-(18)=0
We add all the numbers together, and all the variables
x^2-15x-18=0
a = 1; b = -15; c = -18;
Δ = b2-4ac
Δ = -152-4·1·(-18)
Δ = 297
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:
$\sqrt{\Delta}=\sqrt{297}=\sqrt{9*33}=\sqrt{9}*\sqrt{33}=3\sqrt{33}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-3\sqrt{33}}{2*1}=\frac{15-3\sqrt{33}}{2} $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+3\sqrt{33}}{2*1}=\frac{15+3\sqrt{33}}{2} $

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