9=(7+2x)(5+2x)

Solution for 9=(7+2x)(5+2x) equation:

9=(7+2x)(5+2x)

We move all terms to the left:

9-((7+2x)(5+2x))=0

We add all the numbers together, and all the variables

-((2x+7)(2x+5))+9=0

We multiply parentheses ..

-((+4x^2+10x+14x+35))+9=0


We calculate terms in parentheses: -((+4x^2+10x+14x+35)), so:

(+4x^2+10x+14x+35)

We get rid of parentheses

4x^2+10x+14x+35

We add all the numbers together, and all the variables

4x^2+24x+35

Back to the equation:

-(4x^2+24x+35)


We get rid of parentheses

-4x^2-24x-35+9=0

We add all the numbers together, and all the variables

-4x^2-24x-26=0

a = -4; b = -24; c = -26;
Δ = b2-4ac
Δ = -242-4·(-4)·(-26)
Δ = 160
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:

$\sqrt{\Delta}=\sqrt{160}=\sqrt{16*10}=\sqrt{16}*\sqrt{10}=4\sqrt{10}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-24)-4\sqrt{10}}{2*-4}=\frac{24-4\sqrt{10}}{-8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-24)+4\sqrt{10}}{2*-4}=\frac{24+4\sqrt{10}}{-8}
$