(16x+x)x=90

Solution for (16x+x)x=90 equation:

(16x+x)x=90

We move all terms to the left:

(16x+x)x-(90)=0

We add all the numbers together, and all the variables

(+17x)x-90=0

We multiply parentheses

17x^2-90=0

a = 17; b = 0; c = -90;
Δ = b2-4ac
Δ = 02-4·17·(-90)
Δ = 6120
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:

$\sqrt{\Delta}=\sqrt{6120}=\sqrt{36*170}=\sqrt{36}*\sqrt{170}=6\sqrt{170}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-6\sqrt{170}}{2*17}=\frac{0-6\sqrt{170}}{34}
=-\frac{6\sqrt{170}}{34}
=-\frac{3\sqrt{170}}{17}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+6\sqrt{170}}{2*17}=\frac{0+6\sqrt{170}}{34}
=\frac{6\sqrt{170}}{34}
=\frac{3\sqrt{170}}{17}
$