B=7x2-5x-4x2+5-8x

Solution for B=7x2-5x-4x2+5-8x equation:

=7B^2-5B-4B^2+5-8B

We move all terms to the left:

-(7B^2-5B-4B^2+5-8B)=0

We get rid of parentheses

-7B^2+4B^2+5B+8B-5=0

We add all the numbers together, and all the variables

-3B^2+13B-5=0

a = -3; b = 13; c = -5;
Δ = b2-4ac
Δ = 132-4·(-3)·(-5)
Δ = 109
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$B_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$B_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$B_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(13)-\sqrt{109}}{2*-3}=\frac{-13-\sqrt{109}}{-6}
$
$B_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(13)+\sqrt{109}}{2*-3}=\frac{-13+\sqrt{109}}{-6}
$