-9t^2+72t-135=0

Solution for -9t^2+72t-135=0 equation:

-9t^2+72t-135=0

a = -9; b = 72; c = -135;
Δ = b2-4ac
Δ = 722-4·(-9)·(-135)
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(72)-18}{2*-9}=\frac{-90}{-18}
=+5
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(72)+18}{2*-9}=\frac{-54}{-18}
=+3
$