(2+8x)(4+7x)=0

Solution for (2+8x)(4+7x)=0 equation:

(2+8x)(4+7x)=0

We add all the numbers together, and all the variables

(8x+2)(7x+4)=0

We multiply parentheses ..

(+56x^2+32x+14x+8)=0

We get rid of parentheses

56x^2+32x+14x+8=0

We add all the numbers together, and all the variables

56x^2+46x+8=0

a = 56; b = 46; c = +8;
Δ = b2-4ac
Δ = 462-4·56·8
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(46)-18}{2*56}=\frac{-64}{112}
=-4/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(46)+18}{2*56}=\frac{-28}{112}
=-1/4
$