-7,x+15x2-4=0

Solution for -7,x+15x2-4=0 equation:

-7.x+15x^2-4=0

We add all the numbers together, and all the variables

15x^2-7x-4=0

a = 15; b = -7; c = -4;
Δ = b2-4ac
Δ = -72-4·15·(-4)
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-17}{2*15}=\frac{-10}{30}
=-1/3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+17}{2*15}=\frac{24}{30}
=4/5
$