7.5s^2-3s-10.5=0

Solution for 7.5s^2-3s-10.5=0 equation:

7.5s^2-3s-10.5=0

a = 7.5; b = -3; c = -10.5;
Δ = b2-4ac
Δ = -32-4·7.5·(-10.5)
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-18}{2*7.5}=\frac{-15}{15}
=-1
$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+18}{2*7.5}=\frac{21}{15}
=1+2/5
$