0.3d+7.9=9.1/d

Solution for 0.3d+7.9=9.1/d equation:

0.3d+7.9=9.1/d

We move all terms to the left:

0.3d+7.9-(9.1/d)=0


Domain of the equation: d)!=0

d!=0/1

d!=0

d∈R


We add all the numbers together, and all the variables

0.3d-(+9.1/d)+7.9=0

We get rid of parentheses

0.3d-9.1/d+7.9=0

We multiply all the terms by the denominator


(0.3d)*d+(7.9)*d-9.1=0

We add all the numbers together, and all the variables

(+0.3d)*d+(7.9)*d-9.1=0

We multiply parentheses

0d^2+7.9d-9.1=0

We add all the numbers together, and all the variables

d^2+7.9d-9.1=0

a = 1; b = 7.9; c = -9.1;
Δ = b2-4ac
Δ = 7.92-4·1·(-9.1)
Δ = 98.81
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$d_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7.9)-\sqrt{98.81}}{2*1}=\frac{-7.9-\sqrt{98.81}}{2}
$
$d_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7.9)+\sqrt{98.81}}{2*1}=\frac{-7.9+\sqrt{98.81}}{2}
$