(2a+1)(a)=45

Solution for (2a+1)(a)=45 equation:

(2a+1)(a)=45

We move all terms to the left:

(2a+1)(a)-(45)=0

We multiply parentheses

2a^2+a-45=0

a = 2; b = 1; c = -45;
Δ = b2-4ac
Δ = 12-4·2·(-45)
Δ = 361
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{361}=19$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-19}{2*2}=\frac{-20}{4}
=-5
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+19}{2*2}=\frac{18}{4}
=4+1/2
$