28a^2-32a+21a-24=0

Solution for 28a^2-32a+21a-24=0 equation:

28a^2-32a+21a-24=0

We add all the numbers together, and all the variables

28a^2-11a-24=0

a = 28; b = -11; c = -24;
Δ = b2-4ac
Δ = -112-4·28·(-24)
Δ = 2809
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2809}=53$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-11)-53}{2*28}=\frac{-42}{56}
=-3/4
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-11)+53}{2*28}=\frac{64}{56}
=1+1/7
$