3(x)+45=0.2(x)^2

Solution for 3(x)+45=0.2(x)^2 equation:

3(x)+45=0.2(x)^2

We move all terms to the left:

3(x)+45-(0.2(x)^2)=0

We get rid of parentheses

-0.2x^2+3x+45=0

a = -0.2; b = 3; c = +45;
Δ = b2-4ac
Δ = 32-4·(-0.2)·45
Δ = 45
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{45}=\sqrt{9*5}=\sqrt{9}*\sqrt{5}=3\sqrt{5}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-3\sqrt{5}}{2*-0.2}=\frac{-3-3\sqrt{5}}{-0.4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+3\sqrt{5}}{2*-0.2}=\frac{-3+3\sqrt{5}}{-0.4}
$