-75=-16t2

Solution for -75=-16t2 equation:

-75=-16t^2

We move all terms to the left:

-75-(-16t^2)=0

We get rid of parentheses

16t^2-75=0

a = 16; b = 0; c = -75;
Δ = b2-4ac
Δ = 02-4·16·(-75)
Δ = 4800
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{4800}=\sqrt{1600*3}=\sqrt{1600}*\sqrt{3}=40\sqrt{3}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-40\sqrt{3}}{2*16}=\frac{0-40\sqrt{3}}{32}
=-\frac{40\sqrt{3}}{32}
=-\frac{5\sqrt{3}}{4}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+40\sqrt{3}}{2*16}=\frac{0+40\sqrt{3}}{32}
=\frac{40\sqrt{3}}{32}
=\frac{5\sqrt{3}}{4}
$