3x(x+14)=90

Solution for 3x(x+14)=90 equation:

3x(x+14)=90

We move all terms to the left:

3x(x+14)-(90)=0

We multiply parentheses

3x^2+42x-90=0

a = 3; b = 42; c = -90;
Δ = b2-4ac
Δ = 422-4·3·(-90)
Δ = 2844
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:

$\sqrt{\Delta}=\sqrt{2844}=\sqrt{36*79}=\sqrt{36}*\sqrt{79}=6\sqrt{79}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(42)-6\sqrt{79}}{2*3}=\frac{-42-6\sqrt{79}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(42)+6\sqrt{79}}{2*3}=\frac{-42+6\sqrt{79}}{6}
$