2.1=4.9x^2

Solution for 2.1=4.9x^2 equation:

2.1=4.9x^2

We move all terms to the left:

2.1-(4.9x^2)=0

We get rid of parentheses

-4.9x^2+2.1=0

a = -4.9; b = 0; c = +2.1;
Δ = b2-4ac
Δ = 02-4·(-4.9)·2.1
Δ = 41.16
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{-(0)-\sqrt{41.16}}{2*-4.9}=\frac{0-\sqrt{41.16}}{-9.8}
=-\frac{\sqrt{}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{41.16}}{2*-4.9}=\frac{0+\sqrt{41.16}}{-9.8}
=\frac{\sqrt{}}{-9.8}
$