(3)(4a+6b+3c)+(4c-2b-5a);(4)(x³-3x²y+3xy²)-(x³-3x²y-3xy²-y³)(5)(2a²-½+3a)-4(a-a²+½);(6)½(3x²-4x-2)-¾(x²-2x-1)求解!!!!!!!!!!!!!!!这是整式的运算的题!!!!