-5t^2-60t+320=0

Solution for -5t^2-60t+320=0 equation:

-5t^2-60t+320=0

a = -5; b = -60; c = +320;
Δ = b2-4ac
Δ = -602-4·(-5)·320
Δ = 10000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{10000}=100$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-60)-100}{2*-5}=\frac{-40}{-10}
=+4
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-60)+100}{2*-5}=\frac{160}{-10}
=-16
$