4b*b+15b-4=0

Solution for 4b*b+15b-4=0 equation:

4b*b+15b-4=0

We add all the numbers together, and all the variables

15b+4b*b-4=0

Wy multiply elements

4b^2+15b-4=0

a = 4; b = 15; c = -4;
Δ = b2-4ac
Δ = 152-4·4·(-4)
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$b_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-17}{2*4}=\frac{-32}{8}
=-4
$
$b_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+17}{2*4}=\frac{2}{8}
=1/4
$