-70=-2b(10b-2)

Solution for -70=-2b(10b-2) equation:

-70=-2b(10b-2)

We move all terms to the left:

-70-(-2b(10b-2))=0


We calculate terms in parentheses: -(-2b(10b-2)), so:

-2b(10b-2)

We multiply parentheses

-20b^2+4b

Back to the equation:

-(-20b^2+4b)


We get rid of parentheses

20b^2-4b-70=0

a = 20; b = -4; c = -70;
Δ = b2-4ac
Δ = -42-4·20·(-70)
Δ = 5616
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{5616}=\sqrt{144*39}=\sqrt{144}*\sqrt{39}=12\sqrt{39}$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-4)-12\sqrt{39}}{2*20}=\frac{4-12\sqrt{39}}{40}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-4)+12\sqrt{39}}{2*20}=\frac{4+12\sqrt{39}}{40}
$