(3x-7)*(3x-7)-4*(x+1)*(x+1)=0

Solution for (3x-7)*(3x-7)-4*(x+1)*(x+1)=0 equation:

(3x-7)(3x-7)-4(x+1)(x+1)=0

We multiply parentheses ..

(+9x^2-21x-21x+49)-4(x+1)(x+1)=0

We get rid of parentheses

9x^2-21x-21x-4(x+1)(x+1)+49=0

We multiply parentheses ..

9x^2-4(+x^2+x+x+1)-21x-21x+49=0

We add all the numbers together, and all the variables

9x^2-4(+x^2+x+x+1)-42x+49=0

We multiply parentheses

9x^2-4x^2-4x-4x-42x-4+49=0

We add all the numbers together, and all the variables

5x^2-50x+45=0

a = 5; b = -50; c = +45;
Δ = b2-4ac
Δ = -502-4·5·45
Δ = 1600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1600}=40$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-50)-40}{2*5}=\frac{10}{10}
=1
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-50)+40}{2*5}=\frac{90}{10}
=9
$