197=197-21t-16t^2

Solution for 197=197-21t-16t^2 equation:

197=197-21t-16t^2

We move all terms to the left:

197-(197-21t-16t^2)=0

We get rid of parentheses

16t^2+21t-197+197=0

We add all the numbers together, and all the variables

16t^2+21t=0

a = 16; b = 21; c = 0;
Δ = b2-4ac
Δ = 212-4·16·0
Δ = 441
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{441}=21$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(21)-21}{2*16}=\frac{-42}{32}
=-1+5/16
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(21)+21}{2*16}=\frac{0}{32}
=0
$