(5x的2次方-2x+3)-3(1-2x+x2次方)
=(5x^2-2x+3)-3(1-2x+x^2)
=(5x^2-2x+3)-(3-6x+3x^2)
=5x^2-2x+3-3+6x-3x^2
=2x^2+4x
=2x(x+2）