Y=-4.9x^2+75

Solution for Y=-4.9x^2+75 equation:

=-4.9Y^2+75

We move all terms to the left:

-(-4.9Y^2+75)=0

We get rid of parentheses

4.9Y^2-75=0

a = 4.9; b = 0; c = -75;
Δ = b2-4ac
Δ = 02-4·4.9·(-75)
Δ = 1470
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{1470}=\sqrt{49*30}=\sqrt{49}*\sqrt{30}=7\sqrt{30}$
$Y_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-7\sqrt{30}}{2*4.9}=\frac{0-7\sqrt{30}}{9.8}
=-\frac{7\sqrt{30}}{9.8}
$
$Y_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+7\sqrt{30}}{2*4.9}=\frac{0+7\sqrt{30}}{9.8}
=\frac{7\sqrt{30}}{9.8}
$