X^2-6.5x-10.5=0

Solution for X^2-6.5x-10.5=0 equation:

X^2-6.5X-10.5=0

a = 1; b = -6.5; c = -10.5;
Δ = b2-4ac
Δ = -6.52-4·1·(-10.5)
Δ = 84.25
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{84.25}}{2*1}=\frac{6.5-\sqrt{84.25}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6.5)+\sqrt{84.25}}{2*1}=\frac{6.5+\sqrt{84.25}}{2}
$