28x-40=4x^2

Solution for 28x-40=4x^2 equation:

28x-40=4x^2

We move all terms to the left:

28x-40-(4x^2)=0

determiningTheFunctionDomain
-4x^2+28x-40=0

a = -4; b = 28; c = -40;
Δ = b2-4ac
Δ = 282-4·(-4)·(-40)
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{-(28)-12}{2*-4}=\frac{-40}{-8}
=+5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+12}{2*-4}=\frac{-16}{-8}
=+2
$