5x^2-16=-4x

Solution for 5x^2-16=-4x equation:

5x^2-16=-4x

We move all terms to the left:

5x^2-16-(-4x)=0

We get rid of parentheses

5x^2+4x-16=0

a = 5; b = 4; c = -16;
Δ = b2-4ac
Δ = 42-4·5·(-16)
Δ = 336
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:

$\sqrt{\Delta}=\sqrt{336}=\sqrt{16*21}=\sqrt{16}*\sqrt{21}=4\sqrt{21}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-4\sqrt{21}}{2*5}=\frac{-4-4\sqrt{21}}{10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+4\sqrt{21}}{2*5}=\frac{-4+4\sqrt{21}}{10}
$