-4.9x^2+30x+40=0

Solution for -4.9x^2+30x+40=0 equation:

-4.9x^2+30x+40=0

a = -4.9; b = 30; c = +40;
Δ = b2-4ac
Δ = 302-4·(-4.9)·40
Δ = 1684
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:

$\sqrt{\Delta}=\sqrt{1684}=\sqrt{4*421}=\sqrt{4}*\sqrt{421}=2\sqrt{421}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(30)-2\sqrt{421}}{2*-4.9}=\frac{-30-2\sqrt{421}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(30)+2\sqrt{421}}{2*-4.9}=\frac{-30+2\sqrt{421}}{-9.8}
$