0.9x^2-1.5x-15=0

Solution for 0.9x^2-1.5x-15=0 equation:

0.9x^2-1.5x-15=0

a = 0.9; b = -1.5; c = -15;
Δ = b2-4ac
Δ = -1.52-4·0.9·(-15)
Δ = 56.25
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{-(-1.5)-\sqrt{56.25}}{2*0.9}=\frac{1.5-\sqrt{56.25}}{1.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.5)+\sqrt{56.25}}{2*0.9}=\frac{1.5+\sqrt{56.25}}{1.8}
$