(3+a)(8-2a)=0

Solution for (3+a)(8-2a)=0 equation:

(3+a)(8-2a)=0

We add all the numbers together, and all the variables

(a+3)(-2a+8)=0

We multiply parentheses ..

(-2a^2+8a-6a+24)=0

We get rid of parentheses

-2a^2+8a-6a+24=0

We add all the numbers together, and all the variables

-2a^2+2a+24=0

a = -2; b = 2; c = +24;
Δ = b2-4ac
Δ = 22-4·(-2)·24
Δ = 196
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{196}=14$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(2)-14}{2*-2}=\frac{-16}{-4}
=+4
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(2)+14}{2*-2}=\frac{12}{-4}
=-3
$