3x*4x=28

Solution for 3x*4x=28 equation:

3x*4x=28

We move all terms to the left:

3x*4x-(28)=0

Wy multiply elements

12x^2-28=0

a = 12; b = 0; c = -28;
Δ = b2-4ac
Δ = 02-4·12·(-28)
Δ = 1344
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:

$\sqrt{\Delta}=\sqrt{1344}=\sqrt{64*21}=\sqrt{64}*\sqrt{21}=8\sqrt{21}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-8\sqrt{21}}{2*12}=\frac{0-8\sqrt{21}}{24}
=-\frac{8\sqrt{21}}{24}
=-\frac{\sqrt{21}}{3}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+8\sqrt{21}}{2*12}=\frac{0+8\sqrt{21}}{24}
=\frac{8\sqrt{21}}{24}
=\frac{\sqrt{21}}{3}
$