-3(2+4x)=-7X2

Solution for -3(2+4x)=-7X2 equation:

-3(2+4x)=-7x^2

We move all terms to the left:

-3(2+4x)-(-7x^2)=0

We add all the numbers together, and all the variables

-(-7x^2)-3(4x+2)=0

We multiply parentheses

-(-7x^2)-12x-6=0

We get rid of parentheses

7x^2-12x-6=0

a = 7; b = -12; c = -6;
Δ = b2-4ac
Δ = -122-4·7·(-6)
Δ = 312
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:

$\sqrt{\Delta}=\sqrt{312}=\sqrt{4*78}=\sqrt{4}*\sqrt{78}=2\sqrt{78}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-12)-2\sqrt{78}}{2*7}=\frac{12-2\sqrt{78}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-12)+2\sqrt{78}}{2*7}=\frac{12+2\sqrt{78}}{14}
$