(3x+5)(x+5)=70

Solution for (3x+5)(x+5)=70 equation:

(3x+5)(x+5)=70

We move all terms to the left:

(3x+5)(x+5)-(70)=0

We multiply parentheses ..

(+3x^2+15x+5x+25)-70=0

We get rid of parentheses

3x^2+15x+5x+25-70=0

We add all the numbers together, and all the variables

3x^2+20x-45=0

a = 3; b = 20; c = -45;
Δ = b2-4ac
Δ = 202-4·3·(-45)
Δ = 940
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:

$\sqrt{\Delta}=\sqrt{940}=\sqrt{4*235}=\sqrt{4}*\sqrt{235}=2\sqrt{235}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-2\sqrt{235}}{2*3}=\frac{-20-2\sqrt{235}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+2\sqrt{235}}{2*3}=\frac{-20+2\sqrt{235}}{6}
$