1/3x-x=-7

Solution for 1/3x-x=-7 equation:

1/3x-x=-7

We move all terms to the left:

1/3x-x-(-7)=0


Domain of the equation: 3x!=0

x!=0/3

x!=0

x∈R


We add all the numbers together, and all the variables

-1x+1/3x+7=0

We multiply all the terms by the denominator


-1x*3x+7*3x+1=0

Wy multiply elements

-3x^2+21x+1=0

a = -3; b = 21; c = +1;
Δ = b2-4ac
Δ = 212-4·(-3)·1
Δ = 453
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-\sqrt{453}}{2*-3}=\frac{-21-\sqrt{453}}{-6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+\sqrt{453}}{2*-3}=\frac{-21+\sqrt{453}}{-6}
$