2x(x+4)=70

Solution for 2x(x+4)=70 equation:

2x(x+4)=70

We move all terms to the left:

2x(x+4)-(70)=0

We multiply parentheses

2x^2+8x-70=0

a = 2; b = 8; c = -70;
Δ = b2-4ac
Δ = 82-4·2·(-70)
Δ = 624
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:

$\sqrt{\Delta}=\sqrt{624}=\sqrt{16*39}=\sqrt{16}*\sqrt{39}=4\sqrt{39}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(8)-4\sqrt{39}}{2*2}=\frac{-8-4\sqrt{39}}{4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(8)+4\sqrt{39}}{2*2}=\frac{-8+4\sqrt{39}}{4}
$