7x(2+2x)=84

Solution for 7x(2+2x)=84 equation:

7x(2+2x)=84

We move all terms to the left:

7x(2+2x)-(84)=0

We add all the numbers together, and all the variables

7x(2x+2)-84=0

We multiply parentheses

14x^2+14x-84=0

a = 14; b = 14; c = -84;
Δ = b2-4ac
Δ = 142-4·14·(-84)
Δ = 4900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4900}=70$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(14)-70}{2*14}=\frac{-84}{28}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(14)+70}{2*14}=\frac{56}{28}
=2
$