2.(x^4)^3+(x^3)^2 * x^6-2(x^2)^6=x^(3*4)+x^(3*2)* x^6-2x^(2*6)=x^ 12+x^6*x^6-2x^ 12=x^ 12+x^ 12-2x^ 12=0

3.3x^3*x^4+2x * x^2 * x^4-4x^5*(-x)^2=3x^7+2x^7-4x^5*x^2=5x^7-4x^7=x^7

Ps: x 2 = x the square of x, x 3 = x the cube of X.