9x(x+10)=99

Solution for 9x(x+10)=99 equation:

9x(x+10)=99

We move all terms to the left:

9x(x+10)-(99)=0

We multiply parentheses

9x^2+90x-99=0

a = 9; b = 90; c = -99;
Δ = b2-4ac
Δ = 902-4·9·(-99)
Δ = 11664
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{11664}=108$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(90)-108}{2*9}=\frac{-198}{18}
=-11
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(90)+108}{2*9}=\frac{18}{18}
=1
$