4y2+5y-21=0

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Solution for 4y2+5y-21=0 equation:



4y^2+5y-21=0
a = 4; b = 5; c = -21;
Δ = b2-4ac
Δ = 52-4·4·(-21)
Δ = 361
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{361}=19$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(5)-19}{2*4}=\frac{-24}{8} =-3 $
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(5)+19}{2*4}=\frac{14}{8} =1+3/4 $

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