4x+(15x+3)7x-5=0

Solution for 4x+(15x+3)7x-5=0 equation:

4x+(15x+3)7x-5=0

We multiply parentheses

105x^2+4x+21x-5=0

We add all the numbers together, and all the variables

105x^2+25x-5=0

a = 105; b = 25; c = -5;
Δ = b2-4ac
Δ = 252-4·105·(-5)
Δ = 2725
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{2725}=\sqrt{25*109}=\sqrt{25}*\sqrt{109}=5\sqrt{109}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(25)-5\sqrt{109}}{2*105}=\frac{-25-5\sqrt{109}}{210}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(25)+5\sqrt{109}}{2*105}=\frac{-25+5\sqrt{109}}{210}
$