x^2+12x+3x^2+20=90

Solution for x^2+12x+3x^2+20=90 equation:

x^2+12x+3x^2+20=90

We move all terms to the left:

x^2+12x+3x^2+20-(90)=0

We add all the numbers together, and all the variables

4x^2+12x-70=0

a = 4; b = 12; c = -70;
Δ = b2-4ac
Δ = 122-4·4·(-70)
Δ = 1264
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:

$\sqrt{\Delta}=\sqrt{1264}=\sqrt{16*79}=\sqrt{16}*\sqrt{79}=4\sqrt{79}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-4\sqrt{79}}{2*4}=\frac{-12-4\sqrt{79}}{8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+4\sqrt{79}}{2*4}=\frac{-12+4\sqrt{79}}{8}
$