-x^2-6.5x+10.5625=0

Solution for -x^2-6.5x+10.5625=0 equation:

-x^2-6.5x+10.5625=0

We add all the numbers together, and all the variables

-1x^2-6.5x+10.5625=0

a = -1; b = -6.5; c = +10.5625;
Δ = b2-4ac
Δ = -6.52-4·(-1)·10.5625
Δ = 84.5
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6.5)-\sqrt{84.5}}{2*-1}=\frac{6.5-\sqrt{84.5}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6.5)+\sqrt{84.5}}{2*-1}=\frac{6.5+\sqrt{84.5}}{-2}
$