9x^2-13x-42=0

Solution for 9x^2-13x-42=0 equation:

9x^2-13x-42=0

a = 9; b = -13; c = -42;
Δ = b2-4ac
Δ = -132-4·9·(-42)
Δ = 1681
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1681}=41$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-13)-41}{2*9}=\frac{-28}{18}
=-1+5/9
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-13)+41}{2*9}=\frac{54}{18}
=3
$