(8x)(4,9x)=84

Solution for (8x)(4,9x)=84 equation:

(8x)(4.9x)=84

We move all terms to the left:

(8x)(4.9x)-(84)=0

We add all the numbers together, and all the variables

8x(+4.9x)-84=0

We multiply parentheses

32x^2-84=0

a = 32; b = 0; c = -84;
Δ = b2-4ac
Δ = 02-4·32·(-84)
Δ = 10752
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:

$\sqrt{\Delta}=\sqrt{10752}=\sqrt{256*42}=\sqrt{256}*\sqrt{42}=16\sqrt{42}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-16\sqrt{42}}{2*32}=\frac{0-16\sqrt{42}}{64}
=-\frac{16\sqrt{42}}{64}
=-\frac{\sqrt{42}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+16\sqrt{42}}{2*32}=\frac{0+16\sqrt{42}}{64}
=\frac{16\sqrt{42}}{64}
=\frac{\sqrt{42}}{4}
$