.3x2+7=28

Solution for .3x2+7=28 equation:

.3x^2+7=28

We move all terms to the left:

.3x^2+7-(28)=0

We add all the numbers together, and all the variables

.3x^2-21=0

a = .3; b = 0; c = -21;
Δ = b2-4ac
Δ = 02-4·.3·(-21)
Δ = 25.2
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{-(0)-\sqrt{25.2}}{2*.3}=\frac{0-\sqrt{25.2}}{0.6}
=-\frac{\sqrt{}}{0.6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{25.2}}{2*.3}=\frac{0+\sqrt{25.2}}{0.6}
=\frac{\sqrt{}}{0.6}
$