H=-4.9t2+42t+70

Solution for H=-4.9t2+42t+70 equation:

=-4.9H^2+42H+70

We move all terms to the left:

-(-4.9H^2+42H+70)=0

We get rid of parentheses

4.9H^2-42H-70=0

a = 4.9; b = -42; c = -70;
Δ = b2-4ac
Δ = -422-4·4.9·(-70)
Δ = 3136
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$H_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$H_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3136}=56$
$H_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-42)-56}{2*4.9}=\frac{-14}{9.8}
=-1+3.5/8.16666666667
$
$H_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-42)+56}{2*4.9}=\frac{98}{9.8}
=10
$