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

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

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

We multiply parentheses ..

(+45x^2-35x+36x-28)=0

We get rid of parentheses

45x^2-35x+36x-28=0

We add all the numbers together, and all the variables

45x^2+x-28=0

a = 45; b = 1; c = -28;
Δ = b2-4ac
Δ = 12-4·45·(-28)
Δ = 5041
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{5041}=71$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(1)-71}{2*45}=\frac{-72}{90}
=-4/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+71}{2*45}=\frac{70}{90}
=7/9
$