A=(2x+7)(2x-3)

Solution for A=(2x+7)(2x-3) equation:

=(2A+7)(2A-3)

We move all terms to the left:

-((2A+7)(2A-3))=0

We multiply parentheses ..

-((+4A^2-6A+14A-21))=0


We calculate terms in parentheses: -((+4A^2-6A+14A-21)), so:

(+4A^2-6A+14A-21)

We get rid of parentheses

4A^2-6A+14A-21

We add all the numbers together, and all the variables

4A^2+8A-21

Back to the equation:

-(4A^2+8A-21)


We get rid of parentheses

-4A^2-8A+21=0

a = -4; b = -8; c = +21;
Δ = b2-4ac
Δ = -82-4·(-4)·21
Δ = 400
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{400}=20$
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-20}{2*-4}=\frac{-12}{-8}
=1+1/2
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+20}{2*-4}=\frac{28}{-8}
=-3+1/2
$