14x+5-21x^2=-9-21x^2+14x=-9-521x^2-14x=143x^2-2x=26x^2-4x=46x^2-4x+5=9
14x+5-21x^2=-9得3x^2-2x=26x^-4x+5=2(3x^-2x)+5=9