3.9=-16t^2+124t+30

Solution for 3.9=-16t^2+124t+30 equation:

3.9=-16t^2+124t+30

We move all terms to the left:

3.9-(-16t^2+124t+30)=0

We get rid of parentheses

16t^2-124t-30+3.9=0

We add all the numbers together, and all the variables

16t^2-124t-26.1=0

a = 16; b = -124; c = -26.1;
Δ = b2-4ac
Δ = -1242-4·16·(-26.1)
Δ = 17046.4
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-124)-\sqrt{17046.4}}{2*16}=\frac{124-\sqrt{17046.4}}{32}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-124)+\sqrt{17046.4}}{2*16}=\frac{124+\sqrt{17046.4}}{32}
$