3x²-[5x-(1/2x-3)+2x²]
=3x²-[5x-1/2x+3+2x²]
=3x²-[9/2x+3+2x²]
=3x²-9/2x-3-2x²
=3x²-2x²-9/2x-3
=x²-9/2x-3