A=5x(3x+8)

Solution for A=5x(3x+8) equation:

=5A(3A+8)

We move all terms to the left:

-(5A(3A+8))=0


We calculate terms in parentheses: -(5A(3A+8)), so:

5A(3A+8)

We multiply parentheses

15A^2+40A

Back to the equation:

-(15A^2+40A)


We get rid of parentheses

-15A^2-40A=0

a = -15; b = -40; c = 0;
Δ = b2-4ac
Δ = -402-4·(-15)·0
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-40)-40}{2*-15}=\frac{0}{-30}
=0
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-40)+40}{2*-15}=\frac{80}{-30}
=-2+2/3
$