6=-4.9x^2+8.1x+3

Solution for 6=-4.9x^2+8.1x+3 equation:

6=-4.9x^2+8.1x+3

We move all terms to the left:

6-(-4.9x^2+8.1x+3)=0

We get rid of parentheses

4.9x^2-8.1x-3+6=0

We add all the numbers together, and all the variables

4.9x^2-8.1x+3=0

a = 4.9; b = -8.1; c = +3;
Δ = b2-4ac
Δ = -8.12-4·4.9·3
Δ = 6.81
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{-(-8.1)-\sqrt{6.81}}{2*4.9}=\frac{8.1-\sqrt{6.81}}{9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8.1)+\sqrt{6.81}}{2*4.9}=\frac{8.1+\sqrt{6.81}}{9.8}
$