90=2x(x+4/5x)

Solution for 90=2x(x+4/5x) equation:

90=2x(x+4/5x)

We move all terms to the left:

90-(2x(x+4/5x))=0


Domain of the equation: 5x))!=0

x!=0/1

x!=0

x∈R


We add all the numbers together, and all the variables

-(2x(+x+4/5x))+90=0

We multiply all the terms by the denominator


-(2x(+x+4+90*5x))=0


We calculate terms in parentheses: -(2x(+x+4+90*5x)), so:

2x(+x+4+90*5x)

We add all the numbers together, and all the variables

2x(x+90*5x+4)

We multiply parentheses

2x^2+900x^2+8x

We add all the numbers together, and all the variables

902x^2+8x

Back to the equation:

-(902x^2+8x)


We get rid of parentheses

-902x^2-8x=0

a = -902; b = -8; c = 0;
Δ = b2-4ac
Δ = -82-4·(-902)·0
Δ = 64
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{64}=8$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-8)-8}{2*-902}=\frac{0}{-1804}
=0
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-8)+8}{2*-902}=\frac{16}{-1804}
=-4/451
$