x+2.6x^2=1.4

Solution for x+2.6x^2=1.4 equation:

x+2.6x^2=1.4

We move all terms to the left:

x+2.6x^2-(1.4)=0

We add all the numbers together, and all the variables

2.6x^2+x-1.4=0

a = 2.6; b = 1; c = -1.4;
Δ = b2-4ac
Δ = 12-4·2.6·(-1.4)
Δ = 15.56
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{-(1)-\sqrt{15.56}}{2*2.6}=\frac{-1-\sqrt{15.56}}{5.2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(1)+\sqrt{15.56}}{2*2.6}=\frac{-1+\sqrt{15.56}}{5.2}
$