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X2-20X-84=0
We add all the numbers together, and all the variables
X^2-20X-84=0
a = 1; b = -20; c = -84;
Δ = b2-4ac
Δ = -202-4·1·(-84)
Δ = 736
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}$$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$
The end solution:
$\sqrt{\Delta}=\sqrt{736}=\sqrt{16*46}=\sqrt{16}*\sqrt{46}=4\sqrt{46}$$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-4\sqrt{46}}{2*1}=\frac{20-4\sqrt{46}}{2} $$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+4\sqrt{46}}{2*1}=\frac{20+4\sqrt{46}}{2} $
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