(2x+15)(2x+20)=

Solution for (2x+15)(2x+20)= equation:

(2x+15)(2x+20)=

We move all terms to the left:

(2x+15)(2x+20)-()=0

We add all the numbers together, and all the variables

(2x+15)(2x+20)=0

We multiply parentheses ..

(+4x^2+40x+30x+300)=0

We get rid of parentheses

4x^2+40x+30x+300=0

We add all the numbers together, and all the variables

4x^2+70x+300=0

a = 4; b = 70; c = +300;
Δ = b2-4ac
Δ = 702-4·4·300
Δ = 100
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{100}=10$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(70)-10}{2*4}=\frac{-80}{8}
=-10
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(70)+10}{2*4}=\frac{-60}{8}
=-7+1/2
$