3=-16t^2+28t+5

Solution for 3=-16t^2+28t+5 equation:

3=-16t^2+28t+5

We move all terms to the left:

3-(-16t^2+28t+5)=0

We get rid of parentheses

16t^2-28t-5+3=0

We add all the numbers together, and all the variables

16t^2-28t-2=0

a = 16; b = -28; c = -2;
Δ = b2-4ac
Δ = -282-4·16·(-2)
Δ = 912
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:

$\sqrt{\Delta}=\sqrt{912}=\sqrt{16*57}=\sqrt{16}*\sqrt{57}=4\sqrt{57}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-28)-4\sqrt{57}}{2*16}=\frac{28-4\sqrt{57}}{32}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-28)+4\sqrt{57}}{2*16}=\frac{28+4\sqrt{57}}{32}
$