100=(x+2)(2x+14)

Solution for 100=(x+2)(2x+14) equation:

100=(x+2)(2x+14)

We move all terms to the left:

100-((x+2)(2x+14))=0

We multiply parentheses ..

-((+2x^2+14x+4x+28))+100=0


We calculate terms in parentheses: -((+2x^2+14x+4x+28)), so:

(+2x^2+14x+4x+28)

We get rid of parentheses

2x^2+14x+4x+28

We add all the numbers together, and all the variables

2x^2+18x+28

Back to the equation:

-(2x^2+18x+28)


We get rid of parentheses

-2x^2-18x-28+100=0

We add all the numbers together, and all the variables

-2x^2-18x+72=0

a = -2; b = -18; c = +72;
Δ = b2-4ac
Δ = -182-4·(-2)·72
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-18)-30}{2*-2}=\frac{-12}{-4}
=+3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-18)+30}{2*-2}=\frac{48}{-4}
=-12
$