(x-7.2)(x+1.4)=0

Solution for (x-7.2)(x+1.4)=0 equation:

(x-7.2)(x+1.4)=0

We multiply parentheses ..

(+x^2+1.4x-7.2x-10.08)=0

We get rid of parentheses

x^2+1.4x-7.2x-10.08=0

We add all the numbers together, and all the variables

x^2-5.8x-10.08=0

a = 1; b = -5.8; c = -10.08;
Δ = b2-4ac
Δ = -5.82-4·1·(-10.08)
Δ = 73.96
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5.8)-\sqrt{73.96}}{2*1}=\frac{5.8-\sqrt{73.96}}{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5.8)+\sqrt{73.96}}{2*1}=\frac{5.8+\sqrt{73.96}}{2}
$