4=-16t^2+14t+15

Solution for 4=-16t^2+14t+15 equation:

4=-16t^2+14t+15

We move all terms to the left:

4-(-16t^2+14t+15)=0

We get rid of parentheses

16t^2-14t-15+4=0

We add all the numbers together, and all the variables

16t^2-14t-11=0

a = 16; b = -14; c = -11;
Δ = b2-4ac
Δ = -142-4·16·(-11)
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-14)-30}{2*16}=\frac{-16}{32}
=-1/2
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-14)+30}{2*16}=\frac{44}{32}
=1+3/8
$