(x+1)(x-3)=2x(x+3)

Solution for (x+1)(x-3)=2x(x+3) equation:

(x+1)(x-3)=2x(x+3)

We move all terms to the left:

(x+1)(x-3)-(2x(x+3))=0

We multiply parentheses ..

(+x^2-3x+x-3)-(2x(x+3))=0


We calculate terms in parentheses: -(2x(x+3)), so:

2x(x+3)

We multiply parentheses

2x^2+6x

Back to the equation:

-(2x^2+6x)


We get rid of parentheses

x^2-2x^2-3x+x-6x-3=0

We add all the numbers together, and all the variables

-1x^2-8x-3=0

a = -1; b = -8; c = -3;
Δ = b2-4ac
Δ = -82-4·(-1)·(-3)
Δ = 52
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:

$\sqrt{\Delta}=\sqrt{52}=\sqrt{4*13}=\sqrt{4}*\sqrt{13}=2\sqrt{13}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-2\sqrt{13}}{2*-1}=\frac{8-2\sqrt{13}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+2\sqrt{13}}{2*-1}=\frac{8+2\sqrt{13}}{-2}
$