4k^2+15k=-9

Solution for 4k^2+15k=-9 equation:

4k^2+15k=-9

We move all terms to the left:

4k^2+15k-(-9)=0

We add all the numbers together, and all the variables

4k^2+15k+9=0

a = 4; b = 15; c = +9;
Δ = b2-4ac
Δ = 152-4·4·9
Δ = 81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{81}=9$
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(15)-9}{2*4}=\frac{-24}{8}
=-3
$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(15)+9}{2*4}=\frac{-6}{8}
=-3/4
$