3x^2+5x^2=56

Solution for 3x^2+5x^2=56 equation:

3x^2+5x^2=56

We move all terms to the left:

3x^2+5x^2-(56)=0

We add all the numbers together, and all the variables

8x^2-56=0

a = 8; b = 0; c = -56;
Δ = b2-4ac
Δ = 02-4·8·(-56)
Δ = 1792
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:

$\sqrt{\Delta}=\sqrt{1792}=\sqrt{256*7}=\sqrt{256}*\sqrt{7}=16\sqrt{7}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-16\sqrt{7}}{2*8}=\frac{0-16\sqrt{7}}{16}
=-\frac{16\sqrt{7}}{16}
=-\sqrt{7}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+16\sqrt{7}}{2*8}=\frac{0+16\sqrt{7}}{16}
=\frac{16\sqrt{7}}{16}
=\sqrt{7}
$