4=0.7(x)^2

Solution for 4=0.7(x)^2 equation:

4=0.7(x)^2

We move all terms to the left:

4-(0.7(x)^2)=0

We get rid of parentheses

-0.7x^2+4=0

a = -0.7; b = 0; c = +4;
Δ = b2-4ac
Δ = 02-4·(-0.7)·4
Δ = 11.2
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{11.2}}{2*-0.7}=\frac{0-\sqrt{11.2}}{-1.4}
=-\frac{\sqrt{}}{-1.4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+\sqrt{11.2}}{2*-0.7}=\frac{0+\sqrt{11.2}}{-1.4}
=\frac{\sqrt{}}{-1.4}
$