(x+1)(x+2)=9

Solution for (x+1)(x+2)=9 equation:

(x+1)(x+2)=9

We move all terms to the left:

(x+1)(x+2)-(9)=0

We multiply parentheses ..

(+x^2+2x+x+2)-9=0

We get rid of parentheses

x^2+2x+x+2-9=0

We add all the numbers together, and all the variables

x^2+3x-7=0

a = 1; b = 3; c = -7;
Δ = b2-4ac
Δ = 32-4·1·(-7)
Δ = 37
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(3)-\sqrt{37}}{2*1}=\frac{-3-\sqrt{37}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(3)+\sqrt{37}}{2*1}=\frac{-3+\sqrt{37}}{2}
$