21x2/7=6

Solution for 21x2/7=6 equation:

21x^2/7=6

We move all terms to the left:

21x^2/7-(6)=0

We multiply all the terms by the denominator


21x^2-6*7=0

We add all the numbers together, and all the variables

21x^2-42=0

a = 21; b = 0; c = -42;
Δ = b2-4ac
Δ = 02-4·21·(-42)
Δ = 3528
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{3528}=\sqrt{1764*2}=\sqrt{1764}*\sqrt{2}=42\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-42\sqrt{2}}{2*21}=\frac{0-42\sqrt{2}}{42}
=-\frac{42\sqrt{2}}{42}
=-\sqrt{2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+42\sqrt{2}}{2*21}=\frac{0+42\sqrt{2}}{42}
=\frac{42\sqrt{2}}{42}
=\sqrt{2}
$