5a的2次方-[3a-2(2a-3)-4a的2次方]
=5a²-(3a-4a+6-4a²)
=5a²-(-4a²-a+6)
=5a²+4a²+a-6
=9a²+a-6
3x的2次方-[5x-2(2分之1x-3)+2x的2次方]
=3x²-(5x-x+6+2x²)
=3x²-(2x²+4x+6)
=3x²-2x²-4x-6
=x²-4x-6
5a的2次方-[3a-2(2a-3)-4a的2次方]
=5a²-(3a-4a+6-4a²)
=5a²-(-4a²-a+6)
=5a²+4a²+a-6
=9a²+a-6
3x的2次方-[5x-2(2分之1x-3)+2x的2次方]
=3x²-(5x-x+6+2x²)
=3x²-(2x²+4x+6)
=3x²-2x²-4x-6
=x²-4x-6