①4x²-y²+4x+1 ②（x+2）（x+4）+1 ③x的四次方-3x²-4

：①4x²-y²+4x+1
=4x²+4x+1-y²
=（2x+1)^2-y^2
=(2x+1+y)(2x+1-y)
②（x+2）（x+4）+1
=x^2+6x+8+1
=x^2+6x+9
=(x+3)^2
③x的四次方-3x²-4
=(x^2-4)(x^2+1)
=(x+2)(x-2)(x^2+1)麻烦了，再问道，计算(2x+3y)²(2x-3y)²(2x+3y)²(2x-3y)²=[(2x+3y)(2x-3y)]^2=(4x^2-9y^2)^2=16x^4-72x^2y^2+81y^4