4x^2+8x+16=21

Solution for 4x^2+8x+16=21 equation:

4x^2+8x+16=21

We move all terms to the left:

4x^2+8x+16-(21)=0

We add all the numbers together, and all the variables

4x^2+8x-5=0

a = 4; b = 8; c = -5;
Δ = b2-4ac
Δ = 82-4·4·(-5)
Δ = 144
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{144}=12$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-12}{2*4}=\frac{-20}{8}
=-2+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+12}{2*4}=\frac{4}{8}
=1/2
$