4(4x+5)-(x+5)(x+5)=0

Solution for 4(4x+5)-(x+5)(x+5)=0 equation:

4(4x+5)-(x+5)(x+5)=0

We multiply parentheses

16x-(x+5)(x+5)+20=0

We multiply parentheses ..

-(+x^2+5x+5x+25)+16x+20=0

We get rid of parentheses

-x^2-5x-5x+16x-25+20=0

We add all the numbers together, and all the variables

-1x^2+6x-5=0

a = -1; b = 6; c = -5;
Δ = b2-4ac
Δ = 62-4·(-1)·(-5)
Δ = 16
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{16}=4$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-4}{2*-1}=\frac{-10}{-2}
=+5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+4}{2*-1}=\frac{-2}{-2}
=1
$