0=60-7t-4.90t^2

Solution for 0=60-7t-4.90t^2 equation:

0=60-7t-4.90t^2

We move all terms to the left:

0-(60-7t-4.90t^2)=0

We add all the numbers together, and all the variables

-(60-7t-4.90t^2)=0

We get rid of parentheses

4.90t^2+7t-60=0

a = 4.90; b = 7; c = -60;
Δ = b2-4ac
Δ = 72-4·4.90·(-60)
Δ = 1225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1225}=35$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-35}{2*4.90}=\frac{-42}{9.8}
=-4+2.8/9.8
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+35}{2*4.90}=\frac{28}{9.8}
=2+6/7
$