3(2x+1)(2x-1)-4[(3)/(2)x-3][(3)/(2)+3]=3(4X^2-1)-4(9/4x^2-9)=12x^2-3-9x^2+36=3x^2+335(2x+5)2+(3x-4)(-3x-4)=20x+50-9x^2+16=9x^2+20x+66(2x+y-z+5)(2x-y+z+5)同上，注意平方差公式应用。[(7)/(3)x+(3)/(2)y]2
