7x(2x+6)=0

Solution for 7x(2x+6)=0 equation:

7x(2x+6)=0

We multiply parentheses

14x^2+42x=0

a = 14; b = 42; c = 0;
Δ = b2-4ac
Δ = 422-4·14·0
Δ = 1764
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1764}=42$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(42)-42}{2*14}=\frac{-84}{28}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(42)+42}{2*14}=\frac{0}{28}
=0
$