B=b(5-7b)

Solution for B=b(5-7b) equation:

=B(5-7B)

We move all terms to the left:

-(B(5-7B))=0

We add all the numbers together, and all the variables

-(B(-7B+5))=0


We calculate terms in parentheses: -(B(-7B+5)), so:

B(-7B+5)

We multiply parentheses

-7B^2+5B

Back to the equation:

-(-7B^2+5B)


We get rid of parentheses

7B^2-5B=0

a = 7; b = -5; c = 0;
Δ = b2-4ac
Δ = -52-4·7·0
Δ = 25
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$B_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$B_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{25}=5$
$B_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-5}{2*7}=\frac{0}{14}
=0
$
$B_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+5}{2*7}=\frac{10}{14}
=5/7
$