A=(8x+5)(10x-4)

Solution for A=(8x+5)(10x-4) equation:

=(8A+5)(10A-4)

We move all terms to the left:

-((8A+5)(10A-4))=0

We multiply parentheses ..

-((+80A^2-32A+50A-20))=0


We calculate terms in parentheses: -((+80A^2-32A+50A-20)), so:

(+80A^2-32A+50A-20)

We get rid of parentheses

80A^2-32A+50A-20

We add all the numbers together, and all the variables

80A^2+18A-20

Back to the equation:

-(80A^2+18A-20)


We get rid of parentheses

-80A^2-18A+20=0

a = -80; b = -18; c = +20;
Δ = b2-4ac
Δ = -182-4·(-80)·20
Δ = 6724
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6724}=82$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-18)-82}{2*-80}=\frac{-64}{-160}
=2/5
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-18)+82}{2*-80}=\frac{100}{-160}
=-5/8
$