4x2-20x+21=0

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Solution for 4x2-20x+21=0 equation:



4x^2-20x+21=0
a = 4; b = -20; c = +21;
Δ = b2-4ac
Δ = -202-4·4·21
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-8}{2*4}=\frac{12}{8} =1+1/2 $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+8}{2*4}=\frac{28}{8} =3+1/2 $

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