(4d-1)(d-9)=0

Solution for (4d-1)(d-9)=0 equation:

(4d-1)(d-9)=0

We multiply parentheses ..

(+4d^2-36d-1d+9)=0

We get rid of parentheses

4d^2-36d-1d+9=0

We add all the numbers together, and all the variables

4d^2-37d+9=0

a = 4; b = -37; c = +9;
Δ = b2-4ac
Δ = -372-4·4·9
Δ = 1225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1225}=35$
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-37)-35}{2*4}=\frac{2}{8}
=1/4
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-37)+35}{2*4}=\frac{72}{8}
=9
$