4=0.014x^2-1.21x+28.24

Solution for 4=0.014x^2-1.21x+28.24 equation:

4=0.014x^2-1.21x+28.24

We move all terms to the left:

4-(0.014x^2-1.21x+28.24)=0

We get rid of parentheses

-0.014x^2+1.21x-28.24+4=0

We add all the numbers together, and all the variables

-0.014x^2+1.21x-24.24=0

a = -0.014; b = 1.21; c = -24.24;
Δ = b2-4ac
Δ = 1.212-4·(-0.014)·(-24.24)
Δ = 0.10666
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{-(1.21)-\sqrt{0.10666}}{2*-0.014}=\frac{-1.21-\sqrt{0.10666}}{-0.028}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1.21)+\sqrt{0.10666}}{2*-0.014}=\frac{-1.21+\sqrt{0.10666}}{-0.028}
$