A=5n(n-2)

Solution for A=5n(n-2) equation:

=5A(A-2)

We move all terms to the left:

-(5A(A-2))=0


We calculate terms in parentheses: -(5A(A-2)), so:

5A(A-2)

We multiply parentheses

5A^2-10A

Back to the equation:

-(5A^2-10A)


We get rid of parentheses

-5A^2+10A=0

a = -5; b = 10; c = 0;
Δ = b2-4ac
Δ = 102-4·(-5)·0
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(10)-10}{2*-5}=\frac{-20}{-10}
=+2
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(10)+10}{2*-5}=\frac{0}{-10}
=0
$