b*(b-4.5)=0

Solution for b*(b-4.5)=0 equation:

b(b-4.5)=0

We multiply parentheses

b^2-4.5b=0

a = 1; b = -4.5; c = 0;
Δ = b2-4ac
Δ = -4.52-4·1·0
Δ = 20.25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4.5)-\sqrt{20.25}}{2*1}=\frac{4.5-\sqrt{20.25}}{2}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4.5)+\sqrt{20.25}}{2*1}=\frac{4.5+\sqrt{20.25}}{2}
$