Lời giải :
`b)A=x^4-y^4=(x^2)^2-(y^2)^2=(x^2+y^2)(x^2-y)^2=(x^2+y^2)(x+y)(x-y)`
`b)A=x^2-9y^2=x^2-(3y)^2=(x+3y)(x-3y)`
`b)A=25x^2-9=(5x)^2-3^2=(5x+3)(5x-3)`
`b)A=4x^2-25=(2x)^2-5^2=(2x+5)(2x-5)`
`b)A=4x^2-9y^2=(2x)^2-(3y)^2=(2x+3y)(2x-3y)`
`b)A=9x^4-1/4=(3x^2)^2-(1/2)^2=(3x^2+1/2)(3x^2-1/2)`
`b)A=-x^2/9+x^4=-x^2(1/9-x^2)=-x^2(1/3+x)(1/3-x)`
`b)A=1/25x^2-64y^2=(1/5x)^2-(8y)^2=(1/5x+8y)(1/5x-8y)`
