-4b^2-9b+4=9

Solution for -4b^2-9b+4=9 equation:

-4b^2-9b+4=9

We move all terms to the left:

-4b^2-9b+4-(9)=0

We add all the numbers together, and all the variables

-4b^2-9b-5=0

a = -4; b = -9; c = -5;
Δ = b2-4ac
Δ = -92-4·(-4)·(-5)
Δ = 1
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1}=1$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-9)-1}{2*-4}=\frac{8}{-8}
=-1
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-9)+1}{2*-4}=\frac{10}{-8}
=-1+1/4
$