7y-21/3y=0

Solution for 7y-21/3y=0 equation:

7y-21/3y=0


Domain of the equation: 3y!=0

y!=0/3

y!=0

y∈R


We multiply all the terms by the denominator


7y*3y-21=0

Wy multiply elements

21y^2-21=0

a = 21; b = 0; c = -21;
Δ = b2-4ac
Δ = 02-4·21·(-21)
Δ = 1764
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1764}=42$
$y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-42}{2*21}=\frac{-42}{42}
=-1
$
$y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+42}{2*21}=\frac{42}{42}
=1
$