-(3x²+y)²-(2y+3x)²=

-( 3x²+y)²-(2y+3x)²= -(9x⁴+6x²y+y²)-(4y²+12xy+9x²)=-9x⁴-6x²y-y²-4y²-12xy-9x²=-9x⁴-6x²y-5y²-12xy-9x²