X+(x+1)+(x+2);x=3

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

X+(X+1)+(X+2)X=3

We move all terms to the left:

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

We multiply parentheses

X^2+X+(X+1)+2X-3=0

We get rid of parentheses

X^2+X+X+2X+1-3=0

We add all the numbers together, and all the variables

X^2+4X-2=0

a = 1; b = 4; c = -2;
Δ = b2-4ac
Δ = 42-4·1·(-2)
Δ = 24
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:

$\sqrt{\Delta}=\sqrt{24}=\sqrt{4*6}=\sqrt{4}*\sqrt{6}=2\sqrt{6}$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-2\sqrt{6}}{2*1}=\frac{-4-2\sqrt{6}}{2}
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+2\sqrt{6}}{2*1}=\frac{-4+2\sqrt{6}}{2}
$