3a*3a+a*a-(2a*2a)+(3a-a*a)
=9a²+a²-4a²+3a-a²
=9a²+a²-a²-4a²+3a
=5a²+3a
(2x*2x*2x*2x-5x*5x-4x+1)-(3x*3x*3x-5x*5x-3x)
=16x⁴-25x²-4x+1-27x³+25x²+3x
=16x⁴-27x³+25x²-25x²-4x+3x+1
=16x⁴-27x³-x+1