(4x+9)(7-5x)=0

Solution for (4x+9)(7-5x)=0 equation:

(4x+9)(7-5x)=0

We add all the numbers together, and all the variables

(4x+9)(-5x+7)=0

We multiply parentheses ..

(-20x^2+28x-45x+63)=0

We get rid of parentheses

-20x^2+28x-45x+63=0

We add all the numbers together, and all the variables

-20x^2-17x+63=0

a = -20; b = -17; c = +63;
Δ = b2-4ac
Δ = -172-4·(-20)·63
Δ = 5329
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5329}=73$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-17)-73}{2*-20}=\frac{-56}{-40}
=1+2/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-17)+73}{2*-20}=\frac{90}{-40}
=-2+1/4
$