(x+2)(x-1,35)-3=0

Solution for (x+2)(x-1,35)-3=0 equation:

(x+2)(x-1.35)-3=0

We multiply parentheses ..

(+x^2-1.35x+2x-2.7)-3=0

We get rid of parentheses

x^2-1.35x+2x-2.7-3=0

We add all the numbers together, and all the variables

x^2+0.65x-5.7=0

a = 1; b = 0.65; c = -5.7;
Δ = b2-4ac
Δ = 0.652-4·1·(-5.7)
Δ = 23.2225
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{-(0.65)-\sqrt{23.2225}}{2*1}=\frac{-0.65-\sqrt{23.2225}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0.65)+\sqrt{23.2225}}{2*1}=\frac{-0.65+\sqrt{23.2225}}{2}
$