k+1/4k=15

Solution for k+1/4k=15 equation:

k+1/4k=15

We move all terms to the left:

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


Domain of the equation: 4k!=0

k!=0/4

k!=0

k∈R


We multiply all the terms by the denominator


k*4k-15*4k+1=0

Wy multiply elements

4k^2-60k+1=0

a = 4; b = -60; c = +1;
Δ = b2-4ac
Δ = -602-4·4·1
Δ = 3584
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{3584}=\sqrt{256*14}=\sqrt{256}*\sqrt{14}=16\sqrt{14}$
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-16\sqrt{14}}{2*4}=\frac{60-16\sqrt{14}}{8}
$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+16\sqrt{14}}{2*4}=\frac{60+16\sqrt{14}}{8}
$