K=5x(4x-9)

Solution for K=5x(4x-9) equation:

=5K(4K-9)

We move all terms to the left:

-(5K(4K-9))=0


We calculate terms in parentheses: -(5K(4K-9)), so:

5K(4K-9)

We multiply parentheses

20K^2-45K

Back to the equation:

-(20K^2-45K)


We get rid of parentheses

-20K^2+45K=0

a = -20; b = 45; c = 0;
Δ = b2-4ac
Δ = 452-4·(-20)·0
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$K_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$K_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$K_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(45)-45}{2*-20}=\frac{-90}{-40}
=2+1/4
$
$K_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(45)+45}{2*-20}=\frac{0}{-40}
=0
$