3=(x+4)5x+8

Solution for 3=(x+4)5x+8 equation:

3=(x+4)5x+8

We move all terms to the left:

3-((x+4)5x+8)=0


We calculate terms in parentheses: -((x+4)5x+8), so:

(x+4)5x+8

We multiply parentheses

5x^2+20x+8

Back to the equation:

-(5x^2+20x+8)


We get rid of parentheses

-5x^2-20x-8+3=0

We add all the numbers together, and all the variables

-5x^2-20x-5=0

a = -5; b = -20; c = -5;
Δ = b2-4ac
Δ = -202-4·(-5)·(-5)
Δ = 300
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:

$\sqrt{\Delta}=\sqrt{300}=\sqrt{100*3}=\sqrt{100}*\sqrt{3}=10\sqrt{3}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-20)-10\sqrt{3}}{2*-5}=\frac{20-10\sqrt{3}}{-10}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-20)+10\sqrt{3}}{2*-5}=\frac{20+10\sqrt{3}}{-10}
$