Đáp án+Giải thích các bước giải:

 `39)9x^{4}-24x^{2}+16`

`=(3x^{2})^{2}-2.3x^{2}.4+4^{2}`

`=(3x^{2}-4)^{2}`

`=[(x\sqrt{3})^{2}-2^{2}]^{2}`

`=[(x\sqrt{3}-2).(x\sqrt{3}+2)]^{2}`

`=(x\sqrt{3}-2)^{2}.(x\sqrt{3}+2)^{2}`

`40)x^{4}-12x^{2}y+4y^{2}`

`=(x^{2})^{2}-2.x^{2}.6y+(6y)^{2}+4y^{2}-(6y)^{2}`

`=(x^{2}-6y)^{2}-32y^{2}`

`=(x^{2}-6y)^{2}-(y\sqrt{32})^{2}`

`=(x^{2}-6y-y\sqrt{32}).(x^{2}-6y+y\sqrt{32})`

`=[x^{2}-y.(6+\sqrt{32})].[x^{2}-y.(6-\sqrt{32})]`

`41)4x^{4}-16x^{2}y^{3}+16y^{6}`

`=(2x^{2})^{2}-2.2x^{2}.4y^{3}+(4y^{3})^{2}`

`=(2x^{2}-4y^{3})^{2}`

`=[2.(x^{2}-2y^{3}]^{2}`

`=4.(x^{2}-2y^{3})^{2}`

`42)9x^{4}-12x^{5}+4x^{6}`

`=x^{4}.(9-12x+4x^{2})`

`=x^{4}.[(2x)^{2}-2.2x.3+3^{2}]`

`=x^{4}.(2x-3)^{2}`

`43)x^{10}-4x^{8}+4x^{6}`

`=x^{6}.(x^{4}-4x^{2}+4)`

`=x^{6}.[(x^{2})^{2}-2.x^{2}.2+2^{2}]`

`=x^{6}.(x^{2}-2)^{2}`

`=x^{6}.[x^{2}-(\sqrt{2})^{2}]^{2}`

`=x^{6}.[(x-\sqrt{2}).(x+\sqrt{2})]^{2}`

`=x^{6}.(x-\sqrt{2})^{2}.(x+\sqrt{2})^{2}`

`44)9x^{6}-12x^{7}+4x^{8}`

`=x^{6}.(9-12x+4x^{2})`

`=x^{6}.[(2x)^{2}-2.2x.3+3^{2}]`

`=x^{6}.(2x-3)^{2}`