2x(x-5)=9

Solution for 2x(x-5)=9 equation:

2x(x-5)=9

We move all terms to the left:

2x(x-5)-(9)=0

We multiply parentheses

2x^2-10x-9=0

a = 2; b = -10; c = -9;
Δ = b2-4ac
Δ = -102-4·2·(-9)
Δ = 172
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{172}=\sqrt{4*43}=\sqrt{4}*\sqrt{43}=2\sqrt{43}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-10)-2\sqrt{43}}{2*2}=\frac{10-2\sqrt{43}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-10)+2\sqrt{43}}{2*2}=\frac{10+2\sqrt{43}}{4}
$