A=4x2-7x-3

Solution for A=4x2-7x-3 equation:

=4A^2-7A-3

We move all terms to the left:

-(4A^2-7A-3)=0

We get rid of parentheses

-4A^2+7A+3=0

a = -4; b = 7; c = +3;
Δ = b2-4ac
Δ = 72-4·(-4)·3
Δ = 97
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$A_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-\sqrt{97}}{2*-4}=\frac{-7-\sqrt{97}}{-8}
$
$A_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+\sqrt{97}}{2*-4}=\frac{-7+\sqrt{97}}{-8}
$