a^2-3.5a-1.5=0

Solution for a^2-3.5a-1.5=0 equation:

a^2-3.5a-1.5=0

a = 1; b = -3.5; c = -1.5;
Δ = b2-4ac
Δ = -3.52-4·1·(-1.5)
Δ = 18.25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3.5)-\sqrt{18.25}}{2*1}=\frac{3.5-\sqrt{18.25}}{2}
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3.5)+\sqrt{18.25}}{2*1}=\frac{3.5+\sqrt{18.25}}{2}
$