4x2+21x+5=0*

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Solution for 4x2+21x+5=0* equation:



4x^2+21x+5=0*
We move all terms to the left:
4x^2+21x+5-(0*)=0
We add all the numbers together, and all the variables
4x^2+21x+5-0=0
We add all the numbers together, and all the variables
4x^2+21x+5=0
a = 4; b = 21; c = +5;
Δ = b2-4ac
Δ = 212-4·4·5
Δ = 361
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{361}=19$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-19}{2*4}=\frac{-40}{8} =-5 $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+19}{2*4}=\frac{-2}{8} =-1/4 $

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