Let's first expand the terms on the left side of the equation:

(x^2 - 3x)^2 = (x^2 - 3x)(x^2 - 3x) = x^4 - 3x^3 - 3x^3 + 9x^2 = x^4 - 6x^3 + 9x^2

2(x^2 - 3x) = 2x^2 - 6x

Now substitute these expanded terms back into the original equation:

(x^4 - 6x^3 + 9x^2) - (2x^2 - 6x) = 8

Now simplify the equation:

x^4 - 6x^3 + 9x^2 - 2x^2 + 6x = 8

x^4 - 6x^3 + 7x^2 + 6x - 8 = 0

This is the simplified form of the equation.