x(x^2-2) + 2x^2(x+3) -3x(5x-7)=x(3x^2-9x+17)+2
=> x^3-2x + 2x^3+6x^2 - 15x^2+21x = 3x^3 - 9x^2 +17x +2
=>2x=2
x=1