3=0.3x^2+1.7x+1.5

Solution for 3=0.3x^2+1.7x+1.5 equation:

3=0.3x^2+1.7x+1.5

We move all terms to the left:

3-(0.3x^2+1.7x+1.5)=0

We get rid of parentheses

-0.3x^2-1.7x-1.5+3=0

We add all the numbers together, and all the variables

-0.3x^2-1.7x+1.5=0

a = -0.3; b = -1.7; c = +1.5;
Δ = b2-4ac
Δ = -1.72-4·(-0.3)·1.5
Δ = 4.69
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{4.69}}{2*-0.3}=\frac{1.7-\sqrt{4.69}}{-0.6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.7)+\sqrt{4.69}}{2*-0.3}=\frac{1.7+\sqrt{4.69}}{-0.6}
$