(3.5*x^2)-5*x+1.2=0

Solution for (3.5*x^2)-5*x+1.2=0 equation:

(3.5x^2)-5x+1.2=0

We add all the numbers together, and all the variables

-5x+(3.5x^2)+1.2=0

We get rid of parentheses

3.5x^2-5x+1.2=0

a = 3.5; b = -5; c = +1.2;
Δ = b2-4ac
Δ = -52-4·3.5·1.2
Δ = 8.2
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{-(-5)-\sqrt{8.2}}{2*3.5}=\frac{5-\sqrt{8.2}}{7}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+\sqrt{8.2}}{2*3.5}=\frac{5+\sqrt{8.2}}{7}
$