7x^2+4x-3=90.4

Solution for 7x^2+4x-3=90.4 equation:

7x^2+4x-3=90.4

We move all terms to the left:

7x^2+4x-3-(90.4)=0

We add all the numbers together, and all the variables

7x^2+4x-93.4=0

a = 7; b = 4; c = -93.4;
Δ = b2-4ac
Δ = 42-4·7·(-93.4)
Δ = 2631.2
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(4)-\sqrt{2631.2}}{2*7}=\frac{-4-\sqrt{2631.2}}{14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(4)+\sqrt{2631.2}}{2*7}=\frac{-4+\sqrt{2631.2}}{14}
$