-15k(k+1)=-4

Solution for -15k(k+1)=-4 equation:

-15k(k+1)=-4

We move all terms to the left:

-15k(k+1)-(-4)=0

We add all the numbers together, and all the variables

-15k(k+1)+4=0

We multiply parentheses

-15k^2-15k+4=0

a = -15; b = -15; c = +4;
Δ = b2-4ac
Δ = -152-4·(-15)·4
Δ = 465
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-\sqrt{465}}{2*-15}=\frac{15-\sqrt{465}}{-30}
$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+\sqrt{465}}{2*-15}=\frac{15+\sqrt{465}}{-30}
$