Đáp án:
`2)49-p^4q^2`
`=7^2-(pq)^2`
`=(7-pq)(7+pq)`
`3)a^2x^2-1/4b^2`
`=(ax)^2-(1/2b)^2`
`=(ax-1/2b)(ax+1/2b)`
`5)4p^2-9`
`=(2p)^2-3^2`
`=(2p-3)(2p+3)`
`6)c^2-d^4`
`=c^2-(d^2)^2`
`=(c-d^2)(c+d^2)`
`8)81a^2b^2-9x^2`
`=9(9a^2b^2-x^2)`
`=3[(3ab)^2-x^2]`
`=3(3ab-x)(3ab+x)`
`14)(a-b)^2-1`
`=(a-b-1)(a-b+1)`
`18)1-(x-y)^2`
`=(1-x+y)(1+x-y)`
`20)(4+7a)^2-(8-9c)^2`
`=(4+7a-8+9c)4a+7a+8-9c)`
`=(7a+9c-4)(7a-9c+12)`
`22)a^2-9(b-c)^2`
`=[a-3(b-c)][a+3(b-c)]`
`=(a-3b+3c)(a+3b-3c)`
`26)25p^2m^4-1/36p^4`
`=p^2(25m^2-1/36p^2)`
`=p^2[(5m)^2-(1/6p)^2]`
`=p^2(5m-1/6p)(5m+1/6p)`
`28)x^2+6xy+9y^2`
`=x^2+2.x.3y+(3y)^2`
`=(x+3y)^2`
`30)36p^4+12p^2q^2+q^4`
`=(6p^2)^2+2.6p^2.q^2+(q^2)^2`
`=(6p^2+q^2)^2`
`32)-a^2-2a-1`
`=-(a^2+2a+1)`
`=-(a+1)^2`
`34)25x^4-10x^2y^2+y^4`
`=(5x^2)^2-2.5x^2y^2+(y^2)^2`
`=(5x^2-y^2)^2`
`38)1-q^3`
`=(1-q)(1+q+q^2)`
`40)27b^3-8a^3`
`=(3b)^3-(2a)^3`
`=(3b-2a)(9b^2+6ab+4b^2)`
`42)x^4-64x`
`=x(x^3-64)`
`=x(x^3-4^3)`
`=x(x-4)(x^2+4x+16)`
`44)8x^3+27y^3`
`=(2x)^3+(3y)^3`
`=(2x+3y)(4x^2-6xy+9y^2)`
`46)64x^6-27y^6`
`=(4x^2)^3-(3y^2)^3`
`=(4x^2-3y^2)(16x^4+12x^2y^2+9y^4)`
`50)x^3+9x^2y+27xy^2+27y^3`
`=x^3+3.x^2 .3y+3.x.(3y)^2+(3y)^3`
`=(x+3y)^3`
