5a(15+4a)=0

Solution for 5a(15+4a)=0 equation:

5a(15+4a)=0

We add all the numbers together, and all the variables

5a(4a+15)=0

We multiply parentheses

20a^2+75a=0

a = 20; b = 75; c = 0;
Δ = b2-4ac
Δ = 752-4·20·0
Δ = 5625
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5625}=75$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(75)-75}{2*20}=\frac{-150}{40}
=-3+3/4
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(75)+75}{2*20}=\frac{0}{40}
=0
$