420=(14+2x)(15+2x)

Solution for 420=(14+2x)(15+2x) equation:

420=(14+2x)(15+2x)

We move all terms to the left:

420-((14+2x)(15+2x))=0

We add all the numbers together, and all the variables

-((2x+14)(2x+15))+420=0

We multiply parentheses ..

-((+4x^2+30x+28x+210))+420=0


We calculate terms in parentheses: -((+4x^2+30x+28x+210)), so:

(+4x^2+30x+28x+210)

We get rid of parentheses

4x^2+30x+28x+210

We add all the numbers together, and all the variables

4x^2+58x+210

Back to the equation:

-(4x^2+58x+210)


We get rid of parentheses

-4x^2-58x-210+420=0

We add all the numbers together, and all the variables

-4x^2-58x+210=0

a = -4; b = -58; c = +210;
Δ = b2-4ac
Δ = -582-4·(-4)·210
Δ = 6724
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6724}=82$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-58)-82}{2*-4}=\frac{-24}{-8}
=+3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-58)+82}{2*-4}=\frac{140}{-8}
=-17+1/2
$