A=a^2+24a

Solution for A=a^2+24a equation:

=A^2+24A

We move all terms to the left:

-(A^2+24A)=0

We get rid of parentheses

-A^2-24A=0

We add all the numbers together, and all the variables

-1A^2-24A=0

a = -1; b = -24; c = 0;
Δ = b2-4ac
Δ = -242-4·(-1)·0
Δ = 576
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{576}=24$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-24)-24}{2*-1}=\frac{0}{-2}
=0
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-24)+24}{2*-1}=\frac{48}{-2}
=-24
$