-0.9x^2+1.7x+2.5=0

Solution for -0.9x^2+1.7x+2.5=0 equation:

-0.9x^2+1.7x+2.5=0

a = -0.9; b = 1.7; c = +2.5;
Δ = b2-4ac
Δ = 1.72-4·(-0.9)·2.5
Δ = 11.89
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{-(1.7)-\sqrt{11.89}}{2*-0.9}=\frac{-1.7-\sqrt{11.89}}{-1.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1.7)+\sqrt{11.89}}{2*-0.9}=\frac{-1.7+\sqrt{11.89}}{-1.8}
$