x2+(3x)=700

Solution for x2+(3x)=700 equation:

x2+(3x)=700

We move all terms to the left:

x2+(3x)-(700)=0

We add all the numbers together, and all the variables

x^2+3x-700=0

a = 1; b = 3; c = -700;
Δ = b2-4ac
Δ = 32-4·1·(-700)
Δ = 2809
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2809}=53$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-53}{2*1}=\frac{-56}{2}
=-28
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+53}{2*1}=\frac{50}{2}
=25
$