215=x(8x+3)

Solution for 215=x(8x+3) equation:

215=x(8x+3)

We move all terms to the left:

215-(x(8x+3))=0


We calculate terms in parentheses: -(x(8x+3)), so:

x(8x+3)

We multiply parentheses

8x^2+3x

Back to the equation:

-(8x^2+3x)


We get rid of parentheses

-8x^2-3x+215=0

a = -8; b = -3; c = +215;
Δ = b2-4ac
Δ = -32-4·(-8)·215
Δ = 6889
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{6889}=83$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-83}{2*-8}=\frac{-80}{-16}
=+5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+83}{2*-8}=\frac{86}{-16}
=-5+3/8
$