-0.7x^2+28x=0

Solution for -0.7x^2+28x=0 equation:

-0.7x^2+28x=0

a = -0.7; b = 28; c = 0;
Δ = b2-4ac
Δ = 282-4·(-0.7)·0
Δ = 784
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{784}=28$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(28)-28}{2*-0.7}=\frac{-56}{-1.4}
=+40
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(28)+28}{2*-0.7}=\frac{0}{-1.4}
=0
$