0=-0.01x^2+0.7x+6.4

Solution for 0=-0.01x^2+0.7x+6.4 equation:

0=-0.01x^2+0.7x+6.4

We move all terms to the left:

0-(-0.01x^2+0.7x+6.4)=0

We add all the numbers together, and all the variables

-(-0.01x^2+0.7x+6.4)=0

We get rid of parentheses

0.01x^2-0.7x-6.4=0

a = 0.01; b = -0.7; c = -6.4;
Δ = b2-4ac
Δ = -0.72-4·0.01·(-6.4)
Δ = 0.746
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{-(-0.7)-\sqrt{0.746}}{2*0.01}=\frac{0.7-\sqrt{0.746}}{0.02}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-0.7)+\sqrt{0.746}}{2*0.01}=\frac{0.7+\sqrt{0.746}}{0.02}
$