Đáp án:
j) (x²+y²)²-(1+x²y²)²
=x^4+2x²y²+y^4-(1+2x²y²+x^4y^4)
=x^4+2x²y²+y^4-1-2x²y²-x^4y^4
=x^4+y^4+2x²y²-2x²y²-x^4y^4-1
=x^4+y^4-x^4y^4-1
=x^4-x^4y^4+y^4-1
=x^4(1-y^4)+y^4-1
=-x^4(y^4-1)+y^4-1
=(y^4-1)(1-x^4)
=(y²-1)(y²+1)(1-x²)(1+x²)
l)4x^4+y^4
=(2x²)²-4.x².y²+y^4-4.x².y²
=(2x²-y²)²-(2xy)²
=(2x²-2xy-y²)(2x²-y²+2xy)
b) 9a²-24ab+16b²
=(3a)²-2.3.4.ab+(4b)²
=(3a-4b)²
d) 8x^6-8y^6
=8(x^6-y^6)
=8[(x³)²-(y³)²]
=8[(x³-y³)(x³+y³)]
=8.(x-y)(x²+xy+y²)(x+y)(x²-xy+y²)