1.4x^2+72x-400=0

Solution for 1.4x^2+72x-400=0 equation:

1.4x^2+72x-400=0

a = 1.4; b = 72; c = -400;
Δ = b2-4ac
Δ = 722-4·1.4·(-400)
Δ = 7424
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:

$\sqrt{\Delta}=\sqrt{7424}=\sqrt{256*29}=\sqrt{256}*\sqrt{29}=16\sqrt{29}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(72)-16\sqrt{29}}{2*1.4}=\frac{-72-16\sqrt{29}}{2.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(72)+16\sqrt{29}}{2*1.4}=\frac{-72+16\sqrt{29}}{2.8}
$