(7x)^2+3x=12

Solution for (7x)^2+3x=12 equation:

(7x)^2+3x=12

We move all terms to the left:

(7x)^2+3x-(12)=0

a = 7; b = 3; c = -12;
Δ = b2-4ac
Δ = 32-4·7·(-12)
Δ = 345
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-\sqrt{345}}{2*7}=\frac{-3-\sqrt{345}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+\sqrt{345}}{2*7}=\frac{-3+\sqrt{345}}{14}
$