4(x-2)(7x+5)=0

Solution for 4(x-2)(7x+5)=0 equation:

4(x-2)(7x+5)=0

We multiply parentheses ..

4(+7x^2+5x-14x-10)=0

We multiply parentheses

28x^2+20x-56x-40=0

We add all the numbers together, and all the variables

28x^2-36x-40=0

a = 28; b = -36; c = -40;
Δ = b2-4ac
Δ = -362-4·28·(-40)
Δ = 5776
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5776}=76$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-36)-76}{2*28}=\frac{-40}{56}
=-5/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-36)+76}{2*28}=\frac{112}{56}
=2
$