10x^2+20x-71=9

Solution for 10x^2+20x-71=9 equation:

10x^2+20x-71=9

We move all terms to the left:

10x^2+20x-71-(9)=0

We add all the numbers together, and all the variables

10x^2+20x-80=0

a = 10; b = 20; c = -80;
Δ = b2-4ac
Δ = 202-4·10·(-80)
Δ = 3600
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3600}=60$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(20)-60}{2*10}=\frac{-80}{20}
=-4
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(20)+60}{2*10}=\frac{40}{20}
=2
$