z+1/2z=90

Solution for z+1/2z=90 equation:

z+1/2z=90

We move all terms to the left:

z+1/2z-(90)=0


Domain of the equation: 2z!=0

z!=0/2

z!=0

z∈R


We multiply all the terms by the denominator


z*2z-90*2z+1=0

Wy multiply elements

2z^2-180z+1=0

a = 2; b = -180; c = +1;
Δ = b2-4ac
Δ = -1802-4·2·1
Δ = 32392
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{32392}=\sqrt{4*8098}=\sqrt{4}*\sqrt{8098}=2\sqrt{8098}$
$z_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-180)-2\sqrt{8098}}{2*2}=\frac{180-2\sqrt{8098}}{4}
$
$z_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-180)+2\sqrt{8098}}{2*2}=\frac{180+2\sqrt{8098}}{4}
$