13=49-16t^2

Solution for 13=49-16t^2 equation:

13=49-16t^2

We move all terms to the left:

13-(49-16t^2)=0

We get rid of parentheses

16t^2-49+13=0

We add all the numbers together, and all the variables

16t^2-36=0

a = 16; b = 0; c = -36;
Δ = b2-4ac
Δ = 02-4·16·(-36)
Δ = 2304
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2304}=48$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-48}{2*16}=\frac{-48}{32}
=-1+1/2
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+48}{2*16}=\frac{48}{32}
=1+1/2
$