(b+4)(2b+4)-90=0

Solution for (b+4)(2b+4)-90=0 equation:

(b+4)(2b+4)-90=0

We multiply parentheses ..

(+2b^2+4b+8b+16)-90=0

We get rid of parentheses

2b^2+4b+8b+16-90=0

We add all the numbers together, and all the variables

2b^2+12b-74=0

a = 2; b = 12; c = -74;
Δ = b2-4ac
Δ = 122-4·2·(-74)
Δ = 736
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:

$\sqrt{\Delta}=\sqrt{736}=\sqrt{16*46}=\sqrt{16}*\sqrt{46}=4\sqrt{46}$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-4\sqrt{46}}{2*2}=\frac{-12-4\sqrt{46}}{4}
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+4\sqrt{46}}{2*2}=\frac{-12+4\sqrt{46}}{4}
$