100=-16t^2+400t+100

Solution for 100=-16t^2+400t+100 equation:

100=-16t^2+400t+100

We move all terms to the left:

100-(-16t^2+400t+100)=0

We get rid of parentheses

16t^2-400t-100+100=0

We add all the numbers together, and all the variables

16t^2-400t=0

a = 16; b = -400; c = 0;
Δ = b2-4ac
Δ = -4002-4·16·0
Δ = 160000
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{160000}=400$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-400)-400}{2*16}=\frac{0}{32}
=0
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-400)+400}{2*16}=\frac{800}{32}
=25
$