-4.9x^2-15x+45=0

Solution for -4.9x^2-15x+45=0 equation:

-4.9x^2-15x+45=0

a = -4.9; b = -15; c = +45;
Δ = b2-4ac
Δ = -152-4·(-4.9)·45
Δ = 1107
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:

$\sqrt{\Delta}=\sqrt{1107}=\sqrt{9*123}=\sqrt{9}*\sqrt{123}=3\sqrt{123}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-15)-3\sqrt{123}}{2*-4.9}=\frac{15-3\sqrt{123}}{-9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-15)+3\sqrt{123}}{2*-4.9}=\frac{15+3\sqrt{123}}{-9.8}
$