5=8x^2+7x+4

Solution for 5=8x^2+7x+4 equation:

5=8x^2+7x+4

We move all terms to the left:

5-(8x^2+7x+4)=0

We get rid of parentheses

-8x^2-7x-4+5=0

We add all the numbers together, and all the variables

-8x^2-7x+1=0

a = -8; b = -7; c = +1;
Δ = b2-4ac
Δ = -72-4·(-8)·1
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-9}{2*-8}=\frac{-2}{-16}
=1/8
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+9}{2*-8}=\frac{16}{-16}
=-1
$