7x+4.9x^2-30=0

Solution for 7x+4.9x^2-30=0 equation:

7x+4.9x^2-30=0

a = 4.9; b = 7; c = -30;
Δ = b2-4ac
Δ = 72-4·4.9·(-30)
Δ = 637
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{637}=\sqrt{49*13}=\sqrt{49}*\sqrt{13}=7\sqrt{13}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-7\sqrt{13}}{2*4.9}=\frac{-7-7\sqrt{13}}{9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+7\sqrt{13}}{2*4.9}=\frac{-7+7\sqrt{13}}{9.8}
$