x^2-3x-78.75=0

Solution for x^2-3x-78.75=0 equation:

x^2-3x-78.75=0

a = 1; b = -3; c = -78.75;
Δ = b2-4ac
Δ = -32-4·1·(-78.75)
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-18}{2*1}=\frac{-15}{2}
=-7+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+18}{2*1}=\frac{21}{2}
=10+1/2
$