-85=14t-4.9t^2

Solution for -85=14t-4.9t^2 equation:

-85=14t-4.9t^2

We move all terms to the left:

-85-(14t-4.9t^2)=0

We get rid of parentheses

4.9t^2-14t-85=0

a = 4.9; b = -14; c = -85;
Δ = b2-4ac
Δ = -142-4·4.9·(-85)
Δ = 1862
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:

$\sqrt{\Delta}=\sqrt{1862}=\sqrt{1*1862}=\sqrt{1}*\sqrt{1862}=1\sqrt{1862}$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-14)-1\sqrt{1862}}{2*4.9}=\frac{14-1\sqrt{1862}}{9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-14)+1\sqrt{1862}}{2*4.9}=\frac{14+1\sqrt{1862}}{9.8}
$