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

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

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

We add all the numbers together, and all the variables

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

We multiply parentheses ..

(-8x^2+14x-20x+35)=0

We get rid of parentheses

-8x^2+14x-20x+35=0

We add all the numbers together, and all the variables

-8x^2-6x+35=0

a = -8; b = -6; c = +35;
Δ = b2-4ac
Δ = -62-4·(-8)·35
Δ = 1156
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1156}=34$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-34}{2*-8}=\frac{-28}{-16}
=1+3/4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+34}{2*-8}=\frac{40}{-16}
=-2+1/2
$