0.7=1.3x+x^2

Solution for 0.7=1.3x+x^2 equation:

0.7=1.3x+x^2

We move all terms to the left:

0.7-(1.3x+x^2)=0

We get rid of parentheses

-x^2-1.3x+0.7=0

We add all the numbers together, and all the variables

-1x^2-1.3x+0.7=0

a = -1; b = -1.3; c = +0.7;
Δ = b2-4ac
Δ = -1.32-4·(-1)·0.7
Δ = 4.49
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{-(-1.3)-\sqrt{4.49}}{2*-1}=\frac{1.3-\sqrt{4.49}}{-2}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-1.3)+\sqrt{4.49}}{2*-1}=\frac{1.3+\sqrt{4.49}}{-2}
$