(2x^2-1/2+3x)-4(x-x^2+1/2)
3x^2-[7x-(4x-3)-2x^2]
^后面的数字是指数的意思
(2x^2-1/2+3x)-4(x-x^2+1/2)
3x^2-[7x-(4x-3)-2x^2]
^后面的数字是指数的意思
(2x^2-1/2+3x)-4(x-x^2+1/2)
=2x^2-1/2+3x-4x+4x^2-2
=6x^2-x-5/2
3x^2-[7x-(4x-3)-2x^2]
=3x^2-[7x-4x+3-2x^2]
=3x^2-3x-3+2x^2
=5x^2-3x-3