49=2.3t+4.9t^2

Solution for 49=2.3t+4.9t^2 equation:

49=2.3t+4.9t^2

We move all terms to the left:

49-(2.3t+4.9t^2)=0

We get rid of parentheses

-4.9t^2-2.3t+49=0

a = -4.9; b = -2.3; c = +49;
Δ = b2-4ac
Δ = -2.32-4·(-4.9)·49
Δ = 965.69
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-2.3)-\sqrt{965.69}}{2*-4.9}=\frac{2.3-\sqrt{965.69}}{-9.8}
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-2.3)+\sqrt{965.69}}{2*-4.9}=\frac{2.3+\sqrt{965.69}}{-9.8}
$