7x(X+3)=70

Solution for 7x(X+3)=70 equation:

7x(x+3)=70

We move all terms to the left:

7x(x+3)-(70)=0

We multiply parentheses

7x^2+21x-70=0

a = 7; b = 21; c = -70;
Δ = b2-4ac
Δ = 212-4·7·(-70)
Δ = 2401
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2401}=49$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-49}{2*7}=\frac{-70}{14}
=-5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+49}{2*7}=\frac{28}{14}
=2
$