5x^2-28=13x

Solution for 5x^2-28=13x equation:

5x^2-28=13x

We move all terms to the left:

5x^2-28-(13x)=0

a = 5; b = -13; c = -28;
Δ = b2-4ac
Δ = -132-4·5·(-28)
Δ = 729
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{729}=27$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-13)-27}{2*5}=\frac{-14}{10}
=-1+2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-13)+27}{2*5}=\frac{40}{10}
=4
$